CIS 185 CCNP ROUTE Ch. 4 Manipulating Routing Updates Part 1 - Route Redistribution Rick Graziani Cabrillo College graziani@cabrillo.edu Last Updated: Fall 2015

Objectives Using multiple IP routing protocols Implementing route redistribution Controlling routing update traffic

Multiple Routing Protocols on a Network

Why Run Multiple Routing Protocols? When migrating from an older Interior Gateway Protocol (IGP) to a new IGP. In mixed-router vendor environments, such as EIGRP and OSPF. When the use of a new protocol is desired, but the old routing protocol is still being implemented. When some departments do not want to change support a new routing protocol.

Selecting the Best Route in a Redistribution Environment Cisco routers use the following two parameters to select the best path: Administrative distance: Trustworthiness of the routing source Modifying the administrative distance to influence the route-selection process is discussed later When using route redistribution, you might occasionally need to modify a protocol’s administrative distance so that it is preferred and to prevent routing loops. (later) Routing metric: Best path 1

Multiple Routing Protocols Solutions Summarization Redistribution between routing protocols Route filtering

Route Redistribution

Routing protocols were not designed to interoperate with one another using different: Metrics Reactions to topology changes Timers Processes Routers using different routing protocols can exchange routing information. Route redistribution is the capability of boundary routers connecting different routing domains to exchange and advertise routing information between those routing domains.

One-way route redistribution - one protocol receives the routes from another) Two-way route redistribution - both protocols receive routes from each other. Boundary routers: Routers that perform redistribution Borders two or more ASs or routing domains. Note: The term boundary router is also sometimes used to describe a router running a classful routing protocol (like RIP) that has interfaces in more than one classful network.

Redistribution is always performed outbound The router doing redistribution does not change its routing table. R1 (boundary router) participates in both: OSPF EIGRP Two-way redistribution does not affect the routing table on R1 However: R2 will learn about redistributed EIGRP networks (via OSPF) R3 will learn about redistributed OSPF networks (via EIGRP) Only networks in R1’s routing table can be redistributed.

Configuring Redistribution My best path to 192.100.10.0 is this way. R2 and R3 are running both OSPF and EIGRP Configuring Redistribution 192.168.10.0 R3 R1 OSPF Routing Loop! EIGRP Incompatible routing information Each routing protocol uses different metrics. EIGRP uses slowest BW and cumulative Delay OSPF use cumulative BW Metrics cannot be translated exactly into a different protocol Path selection may not be optimal. Potential Routing loops – Depending on how redistribution is used, routers can send routing information received from one AS back into the AS. (Route Feedback) Inconsistent convergence times: Different routing protocols converge at different rates. These potential trouble spots can be avoided with careful planning and implementation. R2 My best path to 192.100.10.0 is this way.

Concepts of Redistribution

Multiple Routing Processes RTA#show running-config   router ospf 24 network 10.2.0.0 0.0.255.255 area 0 ! router ospf 46 network 192.168.2.0 0.0.0.255 area 2 router eigrp 53 network 172.16.0.0 network 172.17.0.0 router eigrp 141 network 10.0.0.0 network 192.168.3.0 Cisco routers support up to 30 dynamic routing processes on a single router. Most routing protocols allow an administrator to configure multiple processes of the same routing algorithm RIP and BGP are notable exceptions. Not usually recommended Not usually recommended

Route redistribution - The process of exchanging routing information between routing protocols. EIGRP routing domain learns about networks in OSPF routing domain. OSPF routing domain learns about networks in EIGRP routing domain. Done by a boundary router which participates in both routing protocols.

Redistribution Concepts and Processes I run both EIGRP and OSPF. Router(config-router)# redistribute from-protocol [process-id] Note: Other parameters may be required and will be discussed. The redistribution command (“take routes from”) Configured on the boundary router. Participates in both routing protocols. Independent of any one protocol Various complexities depending on the routing protocols and the options. The redistribution command Available for all IP routing protocols, Independent of any one protocol Various complexities depending on the routing protocols and the options. Route redistribution requires at least one router to do the following: At least one “up/up” physical link with each routing domain A working configured routing protocol for each routing domain Redistribution configured for each routing protocol, (redistribute command), Tells the routing protocol to take the routes learned by another source of routing information and then advertise those routes

Redistributing from OSPF into EIGRP

Our Topology OSPF 1 EIGRP 1 Boundary router R2-E-O is running: EIGRP for 172.30.0.0 subnets and 172.31.0.0 network OSPF for 172.16.0.0 subnets and 172.17.0.0 network 192.168.1.0 or 10.0.0.0 not currently included in either routing protocol (more on this later)

Redistribution into EIGRP redistribute protocol [process-id | as-number] [metric bw delay reliability load mtu ] [match {internal | nssa-external | external 1 | external 2}] [tag tag-value] [route-map name] The syntax differs slightly depending on the routing protocol into which routes will be redistributed.

redistribute protocol [process-id | as-number] [metric bw delay reliability load mtu ] [match {internal | nssa-external | external 1 | external 2}] [tag tag-value] [route-map name] protocol - The source of routing information. Includes RIP, OSPF, EIGRP, IS-IS, BGP, connected, and static. process-id, as-number - If redistributing a routing protocol that uses a process-id or ASN on the router global config command, use this parameter to refer to that process or ASN value. metric - A keyword after which follows the four metric components (bandwidth, delay, reliability, link load), plus the MTU associated with the route. match - If redistributing from OSPF, this keyword lets you match internal OSPF routes, external (by type), and NSSA external routes, essentially filtering which routes are redistributed. tag - Assigns a unitless integer value to the route, which can be later matched by other routers using a route-map. route-map - Apply the logic in the referenced route-map to filter routes, set metrics, and set route tags.

Current configurations router eigrp 1 network 172.30.0.0 network 172.31.0.0 auto-summary R2-E-O router eigrp 1 network 172.30.0.0 auto-summary router ospf 1 network 172.16.0.0 0.0.0.3 area 0 R3-O router ospf 1 network 172.16.0.0 0.0.255.255 area 0 R4-O router ospf 1 network 172.16.0.0 0.0.255.255 area 0 network 172.17.0.0 0.0.255.255 area 0

What networks do I know about and how did I learn about them? What do you expect to see? Directly Connected and any EIGRP networks – NO OSPF networks R1-E# show ip route C 172.31.0.0/16 is directly connected, Loopback31 172.30.0.0/16 is variably subnetted, 6 subnets, 3 masks C 172.30.2.0/24 is directly connected, FastEthernet0/1 C 172.30.3.0/24 is directly connected, Loopback0 C 172.30.0.0/30 is directly connected, Serial0/0 D 172.30.0.0/16 is a summary, 00:02:41, Null0 C 172.30.1.0/24 is directly connected, FastEthernet0/0 C 172.30.4.0/24 is directly connected, Loopback1 R1-E#

What do you expect to see? EIGRP and OSPF networks What networks do I know about and how did I learn about them? EIGRP and OSPF networks R2-E-O# show ip route O 172.17.0.0/16 [110/846] via 172.16.0.1, 00:02:32, Serial0/1 172.16.0.0/16 is variably subnetted, 4 subnets, 2 masks O 172.16.0.4/30 [110/845] via 172.16.0.1, 00:02:32, Serial0/1 C 172.16.0.0/30 is directly connected, Serial0/1 O 172.16.1.0/24 [110/782] via 172.16.0.1, 00:02:32, Serial0/1 O 172.16.2.0/24 [110/846] via 172.16.0.1, 00:02:32, Serial0/1 D 172.31.0.0/16 [90/20640000] via 172.30.0.1, 00:03:46, Serial0/0 172.30.0.0/16 is variably subnetted, 5 subnets, 2 masks D 172.30.2.0/24 [90/20514560] via 172.30.0.1, 01:22:36, Serial0/0 D 172.30.3.0/24 [90/20640000] via 172.30.0.1, 01:22:36, Serial0/0 C 172.30.0.0/30 is directly connected, Serial0/0 D 172.30.1.0/24 [90/20514560] via 172.30.0.1, 01:22:36, Serial0/0 D 172.30.4.0/24 [90/20640000] via 172.30.0.1, 01:22:36, Serial0/0 10.0.0.0/24 is subnetted, 1 subnets C 10.0.0.0 is directly connected, FastEthernet0/1 C 192.168.1.0/24 is directly connected, FastEthernet0/0 R2-E-O#

What do you expect to see? What networks do I know about and how did I learn about them? Only OSPF networks – NO EIGRP networks R3-O# show ip route O 172.17.0.0/16 [110/65] via 172.16.0.6, 00:09:06, Serial0/2 172.16.0.0/16 is variably subnetted, 4 subnets, 2 masks C 172.16.0.4/30 is directly connected, Serial0/2 C 172.16.0.0/30 is directly connected, Serial0/1 C 172.16.1.0/24 is directly connected, FastEthernet0/0 O 172.16.2.0/24 [110/65] via 172.16.0.6, 00:09:06, Serial0/2 R3-O#

What do you expect to see? What networks do I know about and how did I learn about them? Only OSPF networks – NO EIGRP networks R4-O# show ip route C 172.17.0.0/16 is directly connected, FastEthernet0/1 172.16.0.0/16 is variably subnetted, 4 subnets, 2 masks C 172.16.0.4/30 is directly connected, Serial0/0 O 172.16.0.0/30 [110/128] via 172.16.0.5, 00:09:52, Serial0/0 O 172.16.1.0/24 [110/65] via 172.16.0.5, 00:09:52, Serial0/0 C 172.16.2.0/24 is directly connected, FastEthernet0/0 R4-0#

Hey! I don’t see any of the networks in the OSPF domain! What happened? No change for R1-E! No OSPF networks Let’s see what happened (or didn’t happen)… I will redistribute my OSPF learned networks (and OSPF network command networks) into EIGRP, telling my EIGRP neighbors about these networks R2-E-O(config)# router eigrp 1 R2-E-O(config-router)# redistribute ospf 1 R1-E# show ip route C 172.31.0.0/16 is directly connected, Loopback31 172.30.0.0/16 is variably subnetted, 6 subnets, 3 masks C 172.30.2.0/24 is directly connected, FastEthernet0/1 C 172.30.3.0/24 is directly connected, Loopback0 C 172.30.0.0/30 is directly connected, Serial0/0 D 172.30.0.0/16 is a summary, 00:02:41, Null0 C 172.30.1.0/24 is directly connected, FastEthernet0/0 C 172.30.4.0/24 is directly connected, Loopback1 R1-E#

Should R2’s routing table change? No R2-E-O# show ip route O 172.17.0.0/16 [110/846] via 172.16.0.1, 00:02:32, Serial0/1 172.16.0.0/16 is variably subnetted, 4 subnets, 2 masks O 172.16.0.4/30 [110/845] via 172.16.0.1, 00:02:32, Serial0/1 C 172.16.0.0/30 is directly connected, Serial0/1 O 172.16.1.0/24 [110/782] via 172.16.0.1, 00:02:32, Serial0/1 O 172.16.2.0/24 [110/846] via 172.16.0.1, 00:02:32, Serial0/1 D 172.31.0.0/16 [90/20640000] via 172.30.0.1, 00:03:46, Serial0/0 172.30.0.0/16 is variably subnetted, 5 subnets, 2 masks D 172.30.2.0/24 [90/20514560] via 172.30.0.1, 01:22:36, Serial0/0 D 172.30.3.0/24 [90/20640000] via 172.30.0.1, 01:22:36, Serial0/0 C 172.30.0.0/30 is directly connected, Serial0/0 D 172.30.1.0/24 [90/20514560] via 172.30.0.1, 01:22:36, Serial0/0 D 172.30.4.0/24 [90/20640000] via 172.30.0.1, 01:22:36, Serial0/0 10.0.0.0/24 is subnetted, 1 subnets C 10.0.0.0 is directly connected, FastEthernet0/1 C 192.168.1.0/24 is directly connected, FastEthernet0/0 R2-E-O#

Metric parameter with redistribute command BW/DLY BW redistribute protocol [process-id | as-number] [metric bw delay reliability load mtu ] default-metric bw delay reliability load mtu When redistributing into EIGRP from another routing protocol you must convert the other routing protocol’s metric (OSPF’s cost, bandwidth) into EIGRP’s metric (BW, DLY, Reliability and Load). This metric, referred to as the seed or default metric, is defined during redistribution configuration. Three methods: Metric parameter with redistribute command Sets the default for all redistribute commands Default-metric command Route-map Sets different metrics for routes learned from a single source

metric parameter takes precedence over the default-metric command 10000 100 255 1 OSPF 1 EIGRP 1 EIGRP 2 router eigrp 1 network 172.20.0.0 redistribute ospf 1 redistribute eigrp 2 default-metric 10000 100 255 1 1500 redistribute rip metric 50000 500 255 1 1500 50000 500 255 1 RIP default-metric command is used where the metric parameter is not being applied in the redistribute command. metric parameter takes precedence over the default-metric command Note: The metric will give all redistributed networks the same starting metric. This is known as the seed metric

1000 33 255 1 R2-E-O(config)# router eigrp 1 R2-E-O(config-router)# redistribute ospf 1 R2-E-O(config-router)# default-metric 1000 33 255 1 1500 BW DLY RLY Load MTU OR R2-E-O(config)# router eigrp 1 R2-E-O(config-router)# redistribute ospf 1 metric 1000 33 255 1 1500 BW DLY RLY Load MTU Note: MTU is NOT one of the EIGRP metrics (never has been, never will be) MTU is included because it is tracked through the path to find the smallest MTU.

EX: External Route (redistributed) Great! Now I see all the networks in the OSPF domain but as EIGRP routes. R1-E# show ip route D EX 172.17.0.0/16 [170/3080448] via 172.30.0.2, 00:01:50, Serial0/0 172.16.0.0/16 is variably subnetted, 4 subnets, 2 masks D EX 172.16.0.4/30 [170/3080448] via 172.30.0.2, 00:01:50, Serial0/0 D EX 172.16.0.0/30 [170/3080448] via 172.30.0.2, 00:01:50, Serial0/0 D EX 172.16.1.0/24 [170/3080448] via 172.30.0.2, 00:01:50, Serial0/0 D EX 172.16.2.0/24 [170/3080448] via 172.30.0.2, 00:01:50, Serial0/0 C 172.31.0.0/16 is directly connected, Loopback31 172.30.0.0/16 is variably subnetted, 6 subnets, 3 masks C 172.30.2.0/24 is directly connected, FastEthernet0/1 C 172.30.3.0/24 is directly connected, Loopback0 C 172.30.0.0/30 is directly connected, Serial0/0 D 172.30.0.0/16 is a summary, 00:12:08, Null0 C 172.30.1.0/24 is directly connected, FastEthernet0/0 C 172.30.4.0/24 is directly connected, Loopback1 EX: External Route (redistributed) 170: Administrative distance (90 for EIGRP internal routes) R1-E has the same metric (3080448) for all external EIGRP networks (from the OSPF domain)

Redistribute command, redistributes the following: R2-E-O# show ip eigrp top P 172.16.0.0/30, 1 successors, FD is 2568448 via Redistributed (2568448/0) R2 redistributed into EIGRP the routes learned via OSPF and its own directly connected network 172.16.0.0/30. But not 192.168.1.0/24 and 10.0.0.0/8 This is because 172.16.0.0/30 is an OSPF enabled interface (network statement) Redistribute command, redistributes the following: All routes in the routing table learned by that routing protocol All connected routes of interfaces on which that routing protocol is enabled Otherwise must be redistributed another way (connected or static) – coming

Two ways to redistribute 10.0.0.0/24 network. What about the 10.0.0.0/24 network? How can I redistribute it into EIGRP? R2-E-O(config)# router ospf 1 R2-E-O(config-router)# network 10.0.0.0 0.0.0.255 area 0 R2-E-O# show ip route 10.0.0.0/24 is subnetted, 1 subnets C 10.0.0.0 is directly connected, FastEthernet0/1 No change to routing table Two ways to redistribute 10.0.0.0/24 network. Redistribute Connected Add OSPF network command Also propagates 10.0.0.0/24 throughout OSPF domain

The 10.0.0.0 network is now included as one of my EIGRP routes. R1-E# show ip route D EX 10.0.0.0 [170/3080448] via 172.30.0.2, 00:01:33, Serial0/0 R4-0# show ip route O 10.0.0.0 [110/129] via 172.16.0.5, 00:04:02, Serial0/0 10.0.0.0 is now redistributed into the EIGRP domain with the rest of the OSPF networks.

What about the 192.168.1.0 network? How can I redistribute it into EIGRP? R2-E-O(config)# router eigrp 1 R2-E-O(config-router)# redistribute connected metric 1000 33 255 1 1500 R1-E# show ip route 10.0.0.0/24 is subnetted, 1 subnets D EX 10.0.0.0 [170/3080448] via 172.30.0.2, 00:01:57, Serial0/0 D EX 192.168.1.0/24 [170/3080448] via 172.30.0.2, 00:01:57, Serial0/0 R1-E# 192.168.1.0/24 is redistributed into EIGRP as a connected network. metric option is not required for this command (default 0, but beyond the scope of this pres.) 192.168.1.0/24 is redistributed into the EIGRP domain using the default metric but it is NOT propagated throughout OSPF domain

R2: Currently router eigrp 1 network 172.30.0.0 auto-summary redistribute ospf 1 default-metric 1000 33 255 1 1500 redistribute connected 1000 33 255 1 1500 ! router ospf 1 network 10.0.0.0 0.0.0.255 area 0 network 172.16.0.0 0.0.0.3 area 0

Redistributing from EIGRP into OSPF

Several similarities and differences to redistributing into EIGRP. BW/DLY BW redistribute protocol [process-id | as-number] [metric {metric-value | transparent}] [metric-type type-value] [match {internal | external 1 | external 2 | nssa-external}] [tag tag-value] [route-map map-tag] [subnets] Several similarities and differences to redistributing into EIGRP. In this case we must convert the EIGRP metric to the Cisco OSPF metric of Bandwidth.

redistribute protocol [process-id | as-number] [metric {metric-value | transparent}] [metric-type type-value] [match {internal | external 1 | external 2 | nssa-external}] [tag tag-value] [route-map map-tag] [subnets] Metric - Defines the cost metric assigned to the route in the Type 5 (or Type 7 if NSSA) LSA. metric transparent when taking from another OSPF process, pass through the metric with the route. metric-type {1 | 2} - Defines the external metric type of 1 (E1 routes) or 2 (E2 routes). Match - If redistributing from OSPF, this keyword lets you match internal OSPF routes, external (by type), and NSSA external routes, essentially filtering which routes are redistributed. Tag - Assigns a unitless integer value to the route, which can be later matched by other routers using a route-map. route-map - Apply the logic in the referenced route-map to filter routes, set metrics, and set route tags. Subnets - Redistribute subnets of classful networks. Without this parameter, only routes for classful networks are redistributed. (This behavior is particular to the OSPF redistribute command.)

Defaults when redistributing into OSPF: BW/DLY BW=20 BW=20 redistribute protocol [process-id | as-number] [metric {metric-value | transparent}] [metric-type type-value] [match {internal | external 1 | external 2 | nssa-external}] [tag tag-value] [route-map map-tag] [subnets] Defaults when redistributing into OSPF: When redistributing networks from all other sources the default metric is 20. External metric type 2 (metric does not change throughout OSPF routing domain) Only redistributes routes of classful (Class A, B, and C) networks, and not for subnets

Where we left off… R2: Currently router eigrp 1 network 172.30.0.0 auto-summary redistribute ospf 1 default-metric 1000 33 255 1 1500 redistribute connected 1000 33 255 1 1500 ! router ospf 1 network 10.0.0.0 0.0.0.255 area 0 network 172.16.0.0 0.0.0.3 area 0 Where we left off…

What do you expect to see? EIGRP and OSPF networks What networks do I know about and how did I learn about them? R2-E-O# show ip route O 172.17.0.0/16 [110/846] via 172.16.0.1, 00:02:32, Serial0/1 172.16.0.0/16 is variably subnetted, 4 subnets, 2 masks O 172.16.0.4/30 [110/845] via 172.16.0.1, 00:02:32, Serial0/1 C 172.16.0.0/30 is directly connected, Serial0/1 O 172.16.1.0/24 [110/782] via 172.16.0.1, 00:02:32, Serial0/1 O 172.16.2.0/24 [110/846] via 172.16.0.1, 00:02:32, Serial0/1 D 172.31.0.0/16 [90/20640000] via 172.30.0.1, 00:03:46, Serial0/0 172.30.0.0/16 is variably subnetted, 5 subnets, 2 masks D 172.30.2.0/24 [90/20514560] via 172.30.0.1, 01:22:36, Serial0/0 D 172.30.3.0/24 [90/20640000] via 172.30.0.1, 01:22:36, Serial0/0 C 172.30.0.0/30 is directly connected, Serial0/0 D 172.30.1.0/24 [90/20514560] via 172.30.0.1, 01:22:36, Serial0/0 D 172.30.4.0/24 [90/20640000] via 172.30.0.1, 01:22:36, Serial0/0 10.0.0.0/24 is subnetted, 1 subnets C 10.0.0.0 is directly connected, FastEthernet0/1 C 192.168.1.0/24 is directly connected, FastEthernet0/0

No EIGRP networks being redistributed into OSPF R2-E-O# show ip ospf data OSPF Router with ID (192.168.1.1) (Process ID 1) Router Link States (Area 0) Link ID ADV Router Age Seq# Checksum Link count 172.16.1.1 172.16.1.1 85 0x80000005 0x006220 5 172.30.0.6 172.30.0.6 2000 0x80000006 0x006BB4 4 192.168.1.1 192.168.1.1 1117 0x80000003 0x009742 3 R2-E-O# No External Type 5 LSAs No EIGRP networks being redistributed into OSPF

Subnets will not be redistributed By default, only classful networks will be redistributed from EIGRP into OSPF. Subnets will not be redistributed Supernets will also be redistributed (such as 173.0.0.0/8) R2-E-O(config)# router ospf 1 R2-E-O(config-router)# redistribute eigrp 1 % Only classful networks will be redistributed R2-E-O(config-router)# R2-E-O# show ip ospf data <Router Link States omitted> Type-5 AS External Link States Link ID ADV Router Age Seq# Checksum Tag 172.31.0.0 192.168.1.1 9 0x80000001 0x0094D4 0 R2-E-O#

Remember, routes are only Redistributed if they are in the Routing table R2-E-O# show ip route O 172.17.0.0/16 [110/846] via 172.16.0.1, 00:03:56, Serial0/1 172.16.0.0/16 is variably subnetted, 4 subnets, 2 masks O 172.16.0.4/30 [110/845] via 172.16.0.1, 00:03:56, Serial0/1 C 172.16.0.0/30 is directly connected, Serial0/1 O 172.16.1.0/24 [110/782] via 172.16.0.1, 00:03:56, Serial0/1 O 172.16.2.0/24 [110/846] via 172.16.0.1, 00:03:56, Serial0/1 D 172.31.0.0/16 [90/20640000] via 172.30.0.1, 00:18:29, Serial0/0 172.30.0.0/16 is variably subnetted, 5 subnets, 2 masks D 172.30.2.0/24 [90/20514560] via 172.30.0.1, 01:37:19, Serial0/0 D 172.30.3.0/24 [90/20640000] via 172.30.0.1, 01:37:19, Serial0/0 C 172.30.0.0/30 is directly connected, Serial0/0 D 172.30.1.0/24 [90/20514560] via 172.30.0.1, 01:37:19, Serial0/0 D 172.30.4.0/24 [90/20640000] via 172.30.0.1, 01:37:19, Serial0/0 10.0.0.0/24 is subnetted, 1 subnets C 10.0.0.0 is directly connected, FastEthernet0/1 C 192.168.1.0/24 is directly connected, FastEthernet0/0

Only the class B network 172.31.0.0/16 is redistributed into OSPF I only see the class B 172.31.0.0/16 network in the EIGRP domain. R3-O# show ip route O 172.17.0.0/16 [110/65] via 172.16.0.6, 00:01:16, Serial0/2 172.16.0.0/16 is variably subnetted, 4 subnets, 2 masks C 172.16.0.4/30 is directly connected, Serial0/2 C 172.16.0.0/30 is directly connected, Serial0/1 C 172.16.1.0/24 is directly connected, FastEthernet0/0 O 172.16.2.0/24 [110/65] via 172.16.0.6, 00:01:16, Serial0/2 O E2 172.31.0.0/16 [110/20] via 172.16.0.2, 00:01:16, Serial0/1 10.0.0.0/24 is subnetted, 1 subnets O 10.0.0.0 [110/65] via 172.16.0.2, 00:01:17, Serial0/1 R3-O# Only the class B network 172.31.0.0/16 is redistributed into OSPF

External Type 5 LSA R3-O# show ip ospf data <Router Link States omitted> Type-5 AS External Link States Link ID ADV Router Age Seq# Checksum Tag 172.31.0.0 192.168.1.1 88 0x80000001 0x0094D4 0 R3-O# External Type 5 LSA

Subnets – Subnets are now included in the redistribution. I will add the subnets option. R2-E-O(config)# router ospf 1 R2-E-O(config-router)# redistribute eigrp 1 subnets No warning message “Only classful networks will be redistributed” Subnets – Subnets are now included in the redistribution.

R2 now includes Type 5 LSAs for subnets R2-E-O# show ip ospf data Type-5 AS External Link States Link ID ADV Router Age Seq# Checksum Tag 172.30.0.0 192.168.1.1 79 0x80000001 0x008EDE 0 172.30.1.0 192.168.1.1 79 0x80000001 0x0095D3 0 172.30.2.0 192.168.1.1 79 0x80000001 0x008ADD 0 172.30.3.0 192.168.1.1 79 0x80000001 0x007FE7 0 172.30.4.0 192.168.1.1 79 0x80000001 0x0074F1 0 172.31.0.0 192.168.1.1 220 0x80000001 0x0094D4 0 R2-E-O# R2 now includes Type 5 LSAs for subnets

Now I see all networks and subnets from the EIGRP domain. R3-O# show ip route O 172.17.0.0/16 [110/65] via 172.16.0.6, 00:13:41, Serial0/2 172.16.0.0/16 is variably subnetted, 4 subnets, 2 masks C 172.16.0.4/30 is directly connected, Serial0/2 C 172.16.0.0/30 is directly connected, Serial0/1 C 172.16.1.0/24 is directly connected, FastEthernet0/0 O 172.16.2.0/24 [110/65] via 172.16.0.6, 00:13:41, Serial0/2 O E2 172.31.0.0/16 [110/20] via 172.16.0.2, 00:13:41, Serial0/1 172.30.0.0/16 is variably subnetted, 5 subnets, 2 masks O E2 172.30.2.0/24 [110/20] via 172.16.0.2, 00:00:12, Serial0/1 O E2 172.30.3.0/24 [110/20] via 172.16.0.2, 00:00:12, Serial0/1 O E2 172.30.0.0/30 [110/20] via 172.16.0.2, 00:00:12, Serial0/1 O E2 172.30.1.0/24 [110/20] via 172.16.0.2, 00:00:14, Serial0/1 O E2 172.30.4.0/24 [110/20] via 172.16.0.2, 00:00:14, Serial0/1 10.0.0.0/24 is subnetted, 1 subnets O 10.0.0.0 [110/65] via 172.16.0.2, 00:00:14, Serial0/1 BW=20 Now I see all networks and subnets from the EIGRP domain. External OSPF routes are E2 with a default cost of 20. metric-type E2 - The cost of a type 2 route is always the external cost, irrespective of the interior cost to reach that route.

External OSPF routes are E2 with a default cost of 20. BW=20 BW=20 R4-0# show ip route C 172.17.0.0/16 is directly connected, FastEthernet0/1 172.16.0.0/16 is variably subnetted, 4 subnets, 2 masks C 172.16.0.4/30 is directly connected, Serial0/0 O 172.16.0.0/30 [110/128] via 172.16.0.5, 00:04:02, Serial0/0 O 172.16.1.0/24 [110/65] via 172.16.0.5, 00:04:02, Serial0/0 C 172.16.2.0/24 is directly connected, FastEthernet0/0 O E2 172.31.0.0/16 [110/20] via 172.16.0.5, 00:04:02, Serial0/0 172.30.0.0/16 is variably subnetted, 5 subnets, 2 masks O E2 172.30.2.0/24 [110/20] via 172.16.0.5, 00:01:46, Serial0/0 O E2 172.30.3.0/24 [110/20] via 172.16.0.5, 00:01:46, Serial0/0 O E2 172.30.0.0/30 [110/20] via 172.16.0.5, 00:01:46, Serial0/0 O E2 172.30.1.0/24 [110/20] via 172.16.0.5, 00:01:46, Serial0/0 O E2 172.30.4.0/24 [110/20] via 172.16.0.5, 00:01:46, Serial0/0 10.0.0.0/24 is subnetted, 1 subnets O 10.0.0.0 [110/129] via 172.16.0.5, 00:04:04, Serial0/0 External OSPF routes are E2 with a default cost of 20. metric-type 2 - The cost of a type 2 route is always the external cost, irrespective of the interior cost to reach that route.

Redistribution into OSPF R4-0# show ip ospf data Type-5 AS External Link States Link ID ADV Router Age Seq# Checksum Tag 172.30.0.0 192.168.1.1 113 0x80000001 0x008EDE 0 172.30.1.0 192.168.1.1 113 0x80000001 0x0095D3 0 172.30.2.0 192.168.1.1 113 0x80000001 0x008ADD 0 172.30.3.0 192.168.1.1 113 0x80000001 0x007FE7 0 172.30.4.0 192.168.1.1 113 0x80000001 0x0074F1 0 172.31.0.0 192.168.1.1 254 0x80000001 0x0094D4 0 R4-0# R4 now includes Type 5 LSAs for subnets

This is okay because 192.168.1.0/24 is a Class C network. R2-E-O(config)#router ospf 1 R2-E-O(config-router)#redistribute connected ? metric Metric for redistributed routes metric-type OSPF/IS-IS exterior metric type for redistributed routes route-map Route map reference subnets Consider subnets for redistribution into OSPF tag Set tag for routes redistributed into OSPF <cr> R2-E-O(config-router)#redistribute connected % Only classful networks will be redistributed R2-E-O(config-router)#redistribute connected subnets Let’s redistribute the 192.168.1.0/24 network into OSPF as a connected network. This is okay because 192.168.1.0/24 is a Class C network. If it was a subnet then…

Redistribution into OSPF R4-0# show ip route <other output omitted> E2 192.168.1.0/24 [110/20] via 172.16.0.5, 00:03:08, Serial0/0 R4-0# show ip ospf data Type-5 AS External Link States Link ID ADV Router Age Seq# Checksum Tag <omitted> 192.168.1.0 192.168.1.1 193 0x80000001 0x0012B8 0 R4-0#

Summary so far… So far… OSPF learned networks are distributed 1000 33 255 1 BW=20 BW=20 Summary so far… R2 summary: router eigrp 1 network 172.30.0.0 auto-summary redistribute ospf 1 default-metric 1000 33 255 1 1500 redistribute connected metric 1000 33 255 1 1500 ! router ospf 1 network 10.0.0.0 0.0.0.255 area 0 network 172.16.0.0 0.0.0.3 area 0 redistribute eigrp 1 subnets redistribute connected OSPF learned networks are distributed into the EIGRP domain Use the metrics for BW DLY RLY Load Distribute any directly connected networks and use these metrics for BW DLY RLY Load So far… EIGRP learned networks are distributed into the OSPF domain, default metric of 20 Distribute any directly connected networks and use default metric of 20

External OSPF routes are E2 with a default cost of 20. R3-O#show ip route O 172.17.0.0/16 [110/65] via 172.16.0.6, 00:13:41, Serial0/2 172.16.0.0/16 is variably subnetted, 4 subnets, 2 masks C 172.16.0.4/30 is directly connected, Serial0/2 C 172.16.0.0/30 is directly connected, Serial0/1 C 172.16.1.0/24 is directly connected, FastEthernet0/0 O 172.16.2.0/24 [110/65] via 172.16.0.6, 00:13:41, Serial0/2 O E2 172.31.0.0/16 [110/20] via 172.16.0.2, 00:13:41, Serial0/1 172.30.0.0/24 is subnetted, 4 subnets O E2 172.30.2.0 [110/20] via 172.16.0.2, 00:11:25, Serial0/1 O E2 172.30.3.0 [110/20] via 172.16.0.2, 00:11:25, Serial0/1 O E2 172.30.1.0 [110/20] via 172.16.0.2, 00:11:25, Serial0/1 O E2 172.30.4.0 [110/20] via 172.16.0.2, 00:11:25, Serial0/1 10.0.0.0/24 is subnetted, 1 subnets O 10.0.0.0 [110/65] via 172.16.0.2, 00:13:43, Serial0/1 O E2 192.168.1.0/24 [110/20] via 172.16.0.2, 00:07:30, Serial0/1 External OSPF routes are E2 with a default cost of 20. metric-type 2 - The cost of a type 2 route is always the external cost, irrespective of the interior cost to reach that route.

External OSPF routes are E2 with a default cost of 20 R4-0#show ip route C 172.17.0.0/16 is directly connected, FastEthernet0/1 172.16.0.0/16 is variably subnetted, 4 subnets, 2 masks C 172.16.0.4/30 is directly connected, Serial0/0 O 172.16.0.0/30 [110/128] via 172.16.0.5, 00:14:05, Serial0/0 O 172.16.1.0/24 [110/65] via 172.16.0.5, 00:14:05, Serial0/0 C 172.16.2.0/24 is directly connected, FastEthernet0/0 O E2 172.31.0.0/16 [110/20] via 172.16.0.5, 00:14:05, Serial0/0 172.30.0.0/24 is subnetted, 4 subnets O E2 172.30.2.0 [110/20] via 172.16.0.5, 00:11:49, Serial0/0 O E2 172.30.3.0 [110/20] via 172.16.0.5, 00:11:49, Serial0/0 O E2 172.30.1.0 [110/20] via 172.16.0.5, 00:11:49, Serial0/0 O E2 172.30.4.0 [110/20] via 172.16.0.5, 00:11:49, Serial0/0 10.0.0.0/24 is subnetted, 1 subnets O 10.0.0.0 [110/129] via 172.16.0.5, 00:14:07, Serial0/0 O E2 192.168.1.0/24 [110/20] via 172.16.0.5, 00:07:54, Serial0/0 External OSPF routes are E2 with a default cost of 20

R2-E-O(config)#router ospf 1 R2-E-O(config-router)#redistribute eigrp 1 subnets metric 100 R2-E-O(config-router)#redistribute connected R4-0#show ip route <external route> O E2 172.31.0.0/16 [110/100] via 172.16.0.5, 00:00:04, Serial0/0 172.30.0.0/24 is subnetted, 4 subnets O E2 172.30.2.0 [110/100] via 172.16.0.5, 00:00:05, Serial0/0 O E2 172.30.3.0 [110/100] via 172.16.0.5, 00:00:05, Serial0/0 O E2 172.30.1.0 [110/100] via 172.16.0.5, 00:00:05, Serial0/0 O E2 172.30.4.0 [110/100] via 172.16.0.5, 00:00:05, Serial0/0 O E2 192.168.1.0/24 [110/20] via 172.16.0.5, 00:12:36, Serial0/0 192.168.1.0/24 still has a cost of 20. Why? It was redistributed with the redistribute connected command without the metric 100 parameter. <redistribute connected metric 100>

Notice that the previous metric 100 parameter is still included! R2-E-O(config)# router ospf 1 R2-E-O(config-router)# redistribute eigrp 1 subnets metric-type 1 R2-E-O# show run router ospf 1 log-adjacency-changes redistribute connected redistribute eigrp 1 metric 100 metric-type 1 subnets network 10.0.0.0 0.0.0.255 area 0 network 172.16.0.0 0.0.0.3 area 0 Notice that the previous metric 100 parameter is still included! metric-type {1 | 2} - Defines the external metric type of 1 (E1 routes) or 2 (E2 routes). metric-type 1 - A type 1 cost is the addition of the external cost and the internal cost used to reach that route. metric-type 2 - The cost of a type 2 route is always the external cost, irrespective of the interior cost to reach that route.

E1 routes, seed metric of 100 plus internal cost. R3-O#show ip route O E1 172.31.0.0/16 [110/164] via 172.16.0.2, 00:00:23, Serial0/1 172.30.0.0/24 is subnetted, 4 subnets O E1 172.30.2.0 [110/164] via 172.16.0.2, 00:00:24, Serial0/1 O E1 172.30.3.0 [110/164] via 172.16.0.2, 00:00:24, Serial0/1 O E1 172.30.1.0 [110/164] via 172.16.0.2, 00:00:24, Serial0/1 O E1 172.30.4.0 [110/164] via 172.16.0.2, 00:00:24, Serial0/1 10.0.0.0/24 is subnetted, 1 subnets O 10.0.0.0 [110/65] via 172.16.0.2, 00:21:45, Serial0/1 O E2 192.168.1.0/24 [110/20] via 172.16.0.2, 00:15:32, Serial0/1 E1 routes, seed metric of 100 plus internal cost. 192.168.1.0/24 still has a cost of 20. It was redistributed with the redistribute connected command without the metric-type 1 parameter, E2 is the default. <redistribute connected metric 100 metric-type 1>

FYI: More on OSPF and External Routes

Redistribution into OSPF EIGRP OSPF Area 0 Area 1 New Topology

Redistribution into OSPF redistribute protocol [process-id | as-number] [metric {metric-value | transparent}] [metric-type type-value] [match {internal | external 1 | external 2 | nssa-external}] [tag tag-value] [route-map map-tag] [subnets] Default if no metric configuration exists Cost 1 for routes learned from BGP Cost 20 for all other route sources default-metric cost OSPF subcommand Setting the default for all redistribute commands metric cost parameters on the redistribute command Setting the metric for one route source Metric transparent parameters on the redistribute command When taking routes from another OSPF process, using the metrics used by that route source Use the route-map parameter on the redistribute command Setting different metrics for routes learned from a single source

Redistribution into OSPF Router that performs redistribution becomes ASBR (Autonomous System Border Router). Injects external routes into OSPF creating a Type 5 LSA for each network/subnet . Type 5 LSA includes: LSID: the subnet number Mask: The subnet mask Advertising router: The RID of the ASBR injecting the route Metric: The metric as set by the ASBR External Metric Type: The external metric type, either 1 or 2

Redistribution into OSPF LSA 5 ASBR floods Type 5 LSAs throughout area. If ABR is: Normal (non-stubby) areas: Flood Type 5 LSAs into area Stub and Totally Stubby areas: No Type 5 LSAs flooded Default route injected by ABR

Redistributing External Type 2 Routes

Redistribution into OSPF LSA 5 Metric = 20 Metric = 20 172.30.26.0/23 E2 route’s metric is simply the metric in the Type 5 LSA. Default = 20 metric parameter R4 has two routes to 172.30.26.0/23: Via R1 Via R8 To avoid loops, OSPF routers use two tiebreaker systems to allow a router to choose a best external route. Router in question resides in the same area as the ASBR (intra-area) Router in question resides in a different area (interarea) than the ASBR

Determining the Next-hop for Type 2 External Routes - Intra-area Metric = 20 Metric = 20 172.30.26.0/23 LSA 5 Router has multiple routes for same E2 destination network: Selects the best route based on the lowest cost to reach any ASBR(s) that advertised the lowest E2 metric. R4: Both routes use metric 20 in this case, so the routes tie. Tiebreaker: Find the advertising ASBR(s) as listed in the Type 5 LSA(s) Using the intra-area LSDB topology calculate the best route to reach the ASBR(s). (This is the route that will be entered into the routing table.) This determines the outgoing interface and next hop based address to to reach the ASBR The route's metric is unchanged in the routing table as listed in theType 5 LSA

Determining the Next-hop for Type 2 External Routes - Intra-area Metric = 20 Metric = 20 172.30.26.0/23 LSA 5 Best path R4 looks in the Type 5 LSA, and sees RID 1.1.1.1 (R1) is the advertising ASBR. R4 then looks at its area 0 LSDB entries, including the Type 1 LSA for RID 1.1.1.1, and calculates all possible area 0 routes to reach 1.1.1.1. R4's best route to reach RID 1.1.1.1 happens to be through its S0/0/0 interface, to next-hop RD1 (172.16.14.1), so R4's route to 172.16.26.0/23 uses these details. The route lists metric 20, as listed in the Type 5 LSA.

Determining the Next-hop for Type 2 External Routes - Interarea 172.30.26.0/23 LSA 5 Metric = 20 Metric = 20 When router is in a different area same issues remain. Different tiebreaker to reach ASBR. Calculation requires more information that previous Intra-area example. To calculate their best route to reach the ASBR, a router in another area: Adds the cost to reach an ABR between the areas Plus that ABR's cost to reach the ASBR

Determining the Next-hop for Type 2 External Routes - Interarea 172.30.26.0/23 64 1 64 64 Best path R5 has two possible routes to reach ASBR: Via R3 Via R4 Although the metric is 20, R5 will use the cost to the ABR PLUS the ABR’s cost to the ASBR to determine the best path. Via R3: 64 + 1 = 65 Via R4: 64 + 64 = 128 R5 chooses the route via R3 because it is a better path (65). The router’s process for doing this is: Calculate the cost to reach the ABR, based on the area's topology database Add the cost from the ABR to the ASBR, as listed in a Type 4 LSA Let’s talk about that Type 4 LSA!

Determining the Next-hop for Type 2 External Routes - Interarea LSA 4: I am ABR R4, I can reach ASBR R1 and my cost to the ASBR is 64. Determining the Next-hop for Type 2 External Routes - Interarea 172.30.26.0/23 LSA 4: I am ABR R3, I can reach ASBR R1 and my cost to the ASBR is 1. LSA 4 The following slides provide additional information on LSA 4s if you are interested... Otherwise The End 

Determining the Next-hop for Type 2 External Routes - Interarea LSA 4: I am ABR R4, I can reach ASBR R1 and my cost to the ASBR is 64. Determining the Next-hop for Type 2 External Routes - Interarea 172.30.26.0/23 LSA 4: I am ABR R3, I can reach ASBR R1 and my cost to the ASBR is 1. LSA 4 Type 4 Summary ASBR LSA: RID of the ASBR RID of the ABR that created and flooded the LSA 4 ABR's cost to reach the ASBR ABRs create Type 4 LSAs after receiving an external Type 5 LSA from an ASBR. ABR forwards a Type 5 LSA into an area ABR looks at the RID of the ASBR that created the Type 5 LSA.. ABR creates a Type 4 LSA listing that ASBR, and the cost to reach that ASBR, flooding that LSA into the neighboring areas.

Determining the Next-hop for Type 2 External Routes - Interarea LSA 4: I am ABR R4, I can reach ASBR R1 and my cost to the ASBR is 64. Determining the Next-hop for Type 2 External Routes - Interarea 172.30.26.0/23 LSA 4: I am ABR R3, I can reach ASBR R1 and my cost to the ASBR is 1. LSA 4 Best path ABR R3 creates and floods Type 4 Summary ASBR LSA into area 1. ASBR 1.1.1.1 (R1), ABR 3.3.3.3 (R3), and cost 1 (R3's cost to reach ASBR). ABR R4 creates and floods Type 4 Summary ASBR LSA into area 1. ASBR 1.1.1.1 (R1), ABR 4.4.4.4 (R4), and lists cost 64 (R4's cost to reach ASBR). When R5 finds two routes for subnet 172.30.26.0/23, and finds both have a metric of 20 Break the tie. For each route: Add intra-area cost to reach the ABR PLUS the ABR's cost to reach the ASBR (as listed in the Type 4 LSA). R5 determines best route is through R3 has the lower cost (65).

Determining the Next-hop for Type 2 External Routes - Interarea LSA 4: I am ABR R4, I can reach ASBR R1 and my cost to the ASBR is 64. Determining the Next-hop for Type 2 External Routes - Interarea 172.30.26.0/23 LSA 4: I am ABR R3, I can reach ASBR R1 and my cost to the ASBR is 1. Best path R5# show ip route O E2 172.30.26.0/23 [110/20] via 172.16.35.3, 05:48:42, Serial0/0

CIS 185 CCNP ROUTE Ch. 4 Manipulating Routing Updates Rick Graziani Cabrillo College graziani@cabrillo.edu