ECMP Routes ECMP (Equal Cost Multi Path) routes have more than one gateway to the same remote network Gateways will be used in Round Robin per SRC/DST address combination
“Check-gateway” option It is possible to force router to check gateway reachability using ICMP (ping) or ARP protocols If gateway is unreachable in a simple route – the route will become inactive If one gateway is unreachable in an ECMP route, only the reachable gateways will be used in the Round Robin algorithm
“Distance” option It is possible to prioritize one route over another if they both point to the same network using “distance” option. When forwarding a packet, the router will use the route with the lowest distance and reachable gateway
ECMP Routing Lab Remake your previously created routes, so that there are two gateways to each of the other participant's local networks 192.168.XY.0/24 and to the Internet Also ensure that “backup link” (next slide) will be used only when all other ways are not accessible
Autonomous System (AS) An autonomous system is a collection of IP networks and routers under the control of one entity (OSPF, iBGP ,RIP) that presents a common routing policy to rest of the network AS is identified by 16 bit number (0 - 65535) Range from 1 to 64511 for use in the Internet Range from 64512 to 65535 for private use