Nanog 14, Atlanta Interesting Peering Activities at the Exchange Points 1 Naiming Shen Cisco Systems

11/9/98Nanog 14, Atlanta2 Peering Activities at NAPs During the Summer of 1997 Pointing default Rewrite eBGP nexthop Passing third party nexthop Misconfiguration

11/9/98Nanog 14, Atlanta3 Case#1: Rewrite eBGP Nexthop Private Peering ISP 3 ISP 1 iMCI ISP 2 cpe2 Mae-East NAP ACLs

11/9/98Nanog 14, Atlanta4 Case#1: Continue... Netflow shown 15% extra traffic from a single subnet traceroute -g shown the traffic coming to us Install a static route of 212.x.x.x pointing to this router and traceroute stopped at ISP1 Install the route in BGP, traceroute shown it coming back to us Thus this router of ISP3 had to rewrite the eBGP nexthop base on the AS numbers This could not be misconfiguration or a simple pointing default. Also this was not just used towards iMCI.

11/9/98Nanog 14, Atlanta5 Case#1: Continue... Install a packet filter on one of the links Install the packet filter on both links, which forced the traffic going to ISP2 After the filter was removed, it came back A New packet filter was applied

11/9/98Nanog 14, Atlanta6 Case #1: Continue... ACL 123 access-list 123 permit icmp x.x.x any access-list 123 permit udp x.x.x any gt access-list 123 permit udp x.x.x any eq 53 access-list 123 deny ip x.x.x any access-list permit ip any any The new filter was there for four days

11/9/98Nanog 14, Atlanta7 ISP 4 iMCI ISP 5 Case#2: Passing 3rd Party Nexthop Peering NAP LAN traffic Peering/customer

11/9/98Nanog 14, Atlanta8 Case#2: Continue... Netflow did not find this case Even you can rewrite the nexthop to your peer’s address, you can’t stop your peer passing your nexthop to the 3rd party route-map command set ip next-hop peer-address Use “next-hop-self”

11/9/98Nanog 14, Atlanta9 ISP 7 iMCI ISP 6 internetMCI.net Case#3: Pointing Default

11/9/98Nanog 14, Atlanta10 Case#3: Continue... It first pointing to ISP6, then to iMCI reverse DNS lookup was xxx.internetmci.net SNMP query had default route MIB value: ip.ipRouteTable.ipRouteEntry.ipRouteNexthop = IpAddress: After we exchanged some , they pointed to someone else

11/9/98Nanog 14, Atlanta11 ISP 9 Case#4: Tunneling ISP 8 ISP 9 GRE NAP1 NAP2

11/9/98Nanog 14, Atlanta12 ISP 11 ISP 10 Upstream Provider NAP3 Case#4: Continue... E1 E3

11/9/98Nanog 14, Atlanta13 Other Activities Run IGP at the NAPs Run Native Multicast Inconsistent route announcement at different peering points Run CDP

11/9/98Nanog 14, Atlanta14 Detection Netflow stats for reverse route lookup and traffic matrix traceroute -g If LSR is disabled, use Ping-Pong trace MAC address accounting

11/9/98Nanog 14, Atlanta15 Filtering Packet level filtering MAC address filtering/rate-limit, sometimes combined with WRED Null out offender’s routes within your domain

11/9/98Nanog 14, Atlanta16 Preventive Measures NAP GIGAswitch L2 filtering NAP ATM PVCs Use “next-hop-self” and reset peer-address Remove non-customer routes from NAP routers Do not carry NAP subnets in the backbone Enforce consistent route announcements