Enhanced Failover of ECMP Static Routes

The enhanced routing features automatically start failover on detection of unreachable next hop gateways for ECMP static routes. It deletes unreachable next-hobs from the routing table to make sure that the required destination is routed only from reachable next-hops. It adds them back when they are reachable.

This functionality probes each next hop gateway of a static route to detect its reachability status. It pings each SGM. If the next hop is unreachable, it is removed from the routing table and re-entered when it is detected as reachable.

Syntax

> set static-route <network>/<subnet_len> ping on

To adjust ping behavior:

> set ping count <val>

> set ping interval <val>

Example

1. Set ECMP for destination 5.5.5.0/24.

   > set static-route 5.5.5.0/24 nexthop gateway address 10.33.85.2 on

   > set static-route 5.5.5.0/24 nexthop gateway address 10.33.85.4 on

   > set static-route 5.5.5.0/24 nexthop gateway address 10.33.85.100 on

   > show route

   1_01:

   Codes: C - Connected, S - Static, R - RIP, B - BGP,

   O - OSPF IntraArea (IA - InterArea, E - External, N - NSSA)

   A - Aggregate, K - Kernel Remnant, H - Hidden, P - Suppressed

   S 0.0.0.0/0 via 192.168.33.1, eth2-01, cost 0, age 2092

   5.5.5.0/24 via 10.33.85.2, eth1-01, cost 0, age 322

   via 10.33.85.4, eth1-01

   via 10.33.85.100, eth1-01

2. Enable failover ECMP on all static routes configured for destination 5.5.5.0/24.

   > set static-route 5.5.5.0/24 ping on

3. Make sure the configuration is correct.

   When next-hop 10.33.85.2 is unreachable (no ICMP replies), after 3 pings (by default) it is removed from the routing table:

   [Expert@CH_Lena-ch02-01]# tcpdump -nepi eth1-01 host 10.33.85.2

   tcpdump: verbose output suppressed, use -v or -vv for full protocol decode

   listening on eth1-01, link-type EN10MB (Ethernet), capture size 96 bytes

   14:40:48.388032 00:1c:7f:a1:01:55 > 00:50:56:a7:7f:f5, ethertype IPv4 (0x0800), length 62: 10.33.85.1 > 10.33.85.2: ICMP echo request, id 53007, seq 43981, length 28

   14:40:58.388425 00:1c:7f:a1:01:55 > 00:50:56:a7:7f:f5, ethertype IPv4 (0x0800), length 62: 10.33.85.1 > 10.33.85.2: ICMP echo request, id 53007, seq 43981, length 28

   14:41:08.387895 00:1c:7f:a1:01:55 > 00:50:56:a7:7f:f5, ethertype IPv4 (0x0800), length 62: 10.33.85.1 > 10.33.85.2: ICMP echo request, id 53007, seq 43981, length 28

   The route is deleted from the routing table.

   01 > show route

   1_01:

   Codes: C - Connected, S - Static, R - RIP, B - BGP,

   O - OSPF IntraArea (IA - InterArea, E - External, N - NSSA)

   A - Aggregate, K - Kernel Remnant, H - Hidden, P - Suppressed

   0.0.0.0/0 via 192.168.33.1, eth2-01, cost 0, age 2511

   S 5.5.5.0/24 via 10.33.85.4, eth1-01, cost 0, age 52

   via 10.33.85.100, eth1-01

   When 10.33.85.2 can be reached again, tcpdump shows that it replies to ping requests and is added to the routing table.

   [Expert@CH_Lena-ch02-01]# tcpdump -nepi eth1-01 host 10.33.85.2

   tcpdump: verbose output suppressed, use -v or -vv for full protocol decode

   listening on eth1-01, link-type EN10MB (Ethernet), capture size 96 bytes

   14:38:08.388224 00:1c:7f:a1:01:55 > 00:50:56:a7:7f:f5, ethertype IPv4 (0x0800), length 62: 10.33.85.1 > 10.33.85.2: ICMP echo request, id 53007, seq 43981, length 28

   14:38:08.388462 00:50:fc:58:80:0a > 00:1c:7f:0f:00:fe, ethertype IPv4 (0x0800), length 62: 10.33.85.2 > 10.33.85.1: ICMP echo reply, id 53007, seq 43981, length 28

   14:38:18.387762 00:1c:7f:a1:01:55 > 00:50:56:a7:7f:f5, ethertype IPv4 (0x0800), length 62: 10.33.85.1 > 10.33.85.2: ICMP echo request, id 53007, seq 43981, length 28

   14:38:18.387980 00:50:fc:58:80:0a > 00:1c:7f:0f:00:fe, ethertype IPv4 (0x0800), length 62: 10.33.85.2 > 10.33.85.1: ICMP echo reply, id 53007, seq 43981, length 28

   14:38:28.388161 00:1c:7f:a1:01:55 > 00:50:56:a7:7f:f5, ethertype IPv4 (0x0800), length 62: 10.33.85.1 > 10.33.85.2: ICMP echo request, id 53007, seq 43981, length 28

   14:38:28.388382 00:50:fc:58:80:0a > 00:1c:7f:0f:00:fe, ethertype IPv4 (0x0800), length 62: 10.33.85.2 > 10.33.85.1: ICMP echo reply, id 53007, seq 43981, length 28

   > show route

   1_01:

   Codes: C - Connected, S - Static, R - RIP, B - BGP,

   O - OSPF IntraArea (IA - InterArea, E - External, N - NSSA)

   A - Aggregate, K - Kernel Remnant, H - Hidden, P - Suppressed

   S 0.0.0.0/0 via 192.168.33.1, eth2-01, cost 0, age 2092

   5.5.5.0/24 via 10.33.85.2, eth1-01, cost 0, age 322

   via 10.33.85.4, eth1-01

   via 10.33.85.100, eth1-01

Validation

1. Run from gclish:

   > show route

2. Make sure that only ECMP static routes with reachable next-hops appear.

   Run: tcpdump

3. Make sure that every few seconds there is a ping request on the interface with static route and ping on.