1. LO:10.10.10.102 PE1 PE2 P1PE3CEA-3 CEA-1 CEA-2 CE-HQ LO:172.16.3.1/32 LO:10.10.10.103 161.142.1.0/30 161.142.1.4/30 161.142.1.8/30.1.2.5.6.9.10 HSRP 192.168.1.1/24 192.168.1.2/24 192.168.1.3/24 VIP: 192.168.1.4 Primary Backup LO:10.10.10.101 LO:172.16.1.1/32 X CEA-1#conf t Enter configuration commands, one per line. End with CNTL/Z. CEA-1(config)#int fa2/0 CEA-1(config-if)#shut *Mar 1 13:45:53.388: %HSRP-6-STATECHANGE: FastEthernet2/0 Grp 0 state Active -> Init *Mar 1 13:45:55.384: %LINK-5-CHANGED: Interface FastEthernet2/0, changed state to administratively down *Mar 1 13:45:56.384: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet2/0, changed state to down CEA-2>sh standby FastEthernet2/0 - Group 0 State is Active 5 state changes, last state change 00:02:07 Virtual IP address is 192.168.1.4 Active virtual MAC address is 0000.0c07.ac00 Local virtual MAC address is 0000.0c07.ac00 (v1 default) Hello time 3 sec, hold time 10 sec192.168.1.4 Next hello sent in 1.460 secs Preemption enabled, delay min 10 secs Active router is local Standby router is unknown Priority 100 (default 100) Track interface Serial0/0 state Up decrement 10 IP redundancy name is "hsrp-Fa2/0-0" (default)

2. LO:10.10.10.102 PE1 PE2 P1PE3CEA-3 CEA-1 CEA-2 CE-HQ LO:172.16.3.1/32 LO:10.10.10.103 161.142.1.0/30 161.142.1.4/30 161.142.1.8/30.1.2.5.6.9.10 HSRP 192.168.1.1/24 192.168.1.2/24 192.168.1.3/24 VIP: 192.168.1.4 Primary Backup LO:10.10.10.101 LO:172.16.1.1/32 X EHQ#ping 172.16.3.1 source 172.16.1.1172.16.3.1172.16.1.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.16.3.1, timeout is 2 seconds: Packet sent with a source address of 172.16.1.1..... Success rate is 0 percent (0/5)172.16.3.1172.16.1.1 CEHQ#sh ip int brief interface IP-Address OK? Method Status Protocol FastEthernet0/0 192.168.1.3 YES manual up up Loopback0 172.16.1.1 YES manual up up 192.168.1.3172.16.1.1 CEHQ#tr 172.16.3.1 source 172.16.1.1 numeric Type escape sequence to abort. Tracing the route to 172.16.3.1172.16.3.1172.16.1.1172.16.3.1 1 192.168.1.2 16 msec 20 msec 16 msec 2 161.142.1.5 12 msec 36 msec 40 msec 3 * * * 4 * * * 5 * * *192.168.1.2161.142.1.5 CEA-1#sh standby FastEthernet2/0 - Group 0 State is Active 5 state changes, last state change 12:18:31 Virtual IP address is 192.168.1.4 Active virtual MAC address is 0000.0c07.ac00 Local virtual MAC address is 0000.0c07.ac00 (v1 default) Hello time 3 sec, hold time 10 sec192.168.1.4 Next hello sent in 1.016 secs Preemption enabled, delay min 10 secs Active router is local Standby router is 192.168.1.2, priority 100 (expires in 8.696 sec)192.168.1.2 Priority 100 (default 100) Track interface Serial0/0 state Up decrement 10 IP redundancy name is "hsrp-Fa2/0-0" (default)

3. LO:10.10.10.102 PE1 PE2 P1PE3CEA-3 CEA-1 CEA-2 CE-HQ LO:172.16.3.1/32 LO:10.10.10.103 161.142.1.0/30 161.142.1.4/30 161.142.1.8/30.1.2.5.6.9.10 HSRP 192.168.1.1/24 192.168.1.2/24 192.168.1.3/24 VIP: 192.168.1.4 Primary Backup LO:10.10.10.101 LO:172.16.1.1/32 CEA-3#sh ip int brief Interface IP-Address OK? Method Status Protocol Serial0/0 161.142.1.10 YES NVRAM up up Loopback0 172.16.3.1 YES manual up up CEA-3#ping 172.16.1.1 source 172.16.3.1161.142.1.10172.16.3.1172.16.1.1172.16.3.1 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.16.1.1, timeout is 2 seconds: Packet sent with a source address of 172.16.3.1 U.U.U Success rate is 0 percent (0/5)172.16.1.1172.16.3.1 CEA-3#tr 172.16.1.1 source 172.16.3.1 numeric Type escape sequence to abort. Tracing the route to 172.16.1.1172.16.1.1172.16.3.1172.16.1.1 1 161.142.1.9 16 msec 4 msec 8 msec 2 10.10.10.9 12 msec 56 msec 28 msec 3 161.142.1.1 76 msec 64 msec 36 msec 4 161.142.1.2 88 msec 36 msec 68 msec 5 161.142.1.2 !H * !H161.142.1.910.10.10.9161.142.1.1161.142.1.2 X Output: Even though the link of CEA-1 down, the PE1 is up, traffic got black holed at CEA-1

4. LO:10.10.10.102 PE1 PE2 P1PE3CEA-3 CEA-1 CEA-2 CE-HQ LO:172.16.3.1/32 LO:10.10.10.103 161.142.1.0/30 161.142.1.4/30 161.142.1.8/30.1.2.5.6.9.10 HSRP 192.168.1.1/24 192.168.1.2/24 192.168.1.3/24 VIP: 192.168.1.4 Primary Backup LO:10.10.10.101 LO:172.16.1.1/32 X PE3-AS1#sh ip bgp vpn vrf CustomerA 172.16.1.1172.16.1.1 BGP routing table entry for 1:100:172.16.1.1/32, version 28 Paths: (2 available, best #1, table CustomerA)172.16.1.1/32 Not advertised to any peer Local 10.10.10.101 (metric 129) from 10.10.10.101 (10.10.10.101) Origin incomplete, metric 0, localpref 100, valid, internal, best Extended Community: RT:1:100, mpls labels in/out nolabel/21 Local 10.10.10.102 (metric 129) from 10.10.10.102 (10.10.10.102) Origin incomplete, metric 0, localpref 100, valid, internal Extended Community: RT:1:100,10.10.10.101 10.10.10.102 mpls labels in/out nolabel/22 PE1-AS1>sh ip bgp vpn vrf CustomerA 172.16.1.1172.16.1.1 BGP routing table entry for 1:100:172.16.1.1/32, version 29 Paths: (2 available, best #1, table CustomerA) Advertised to update-groups: 1 Local 161.142.1.2 from 0.0.0.0 (10.10.10.101) Origin incomplete, metric 0, localpref 100, weight 32768, valid, sourced, best Extended Community: RT:1:100, mpls labels in/out 21/nolabel Local 10.10.10.102 (metric 129) from 10.10.10.102 ( 10.10.10.102) Origin incomplete, metric 0, localpref 100, valid, internal Extended Community: RT:1:100, mpls labels in/out 21/22172.16.1.1/32161.142.1.20.0.0.010.10.10.10110.10.10.102 From PE perspective, it seems that, the traffic still prefer via CEA-1 PE1