Symptom

Topology : 9372-1 e1/49 ——————e4/49 9500 e4/50——————— e1/49 9372-2 EIGRP peering : 9372-1 (SVI 8) ——— (SVI 8) 9500 (SVI 6)———— (SVI 6) 9372-2 Routes on 9500 : ================ 9500# sh ip route IP Route Table for VRF "default" '*' denotes best ucast next-hop '**' denotes best mcast next-hop '[x/y]' denotes [preference/metric] '%' in via output denotes VRF 0.0.0.0/0, ubest/mbest: 1/0 *via 4.4.4.1, [200/0], 00:00:24, bgp-1, internal, tag 1 4.4.4.0/24, ubest/mbest: 1/0, attached *via 4.4.4.2, Vlan4, [0/0], 00:00:24, direct 4.4.4.2/32, ubest/mbest: 1/0, attached *via 4.4.4.2, Vlan4, [0/0], 00:00:24, local 6.6.6.0/24, ubest/mbest: 1/0, attached *via 6.6.6.2, Vlan6, [0/0], 00:00:24, direct 6.6.6.2/32, ubest/mbest: 1/0, attached *via 6.6.6.2, Vlan6, [0/0], 00:00:24, local 8.8.8.0/24, ubest/mbest: 1/0, attached *via 8.8.8.2, Vlan8, [0/0], 00:00:24, direct 8.8.8.2/32, ubest/mbest: 1/0, attached *via 8.8.8.2, Vlan8, [0/0], 00:00:24, local Routes on 9372-2 : ===================== 9372-2(config-if)# sh ip route IP Route Table for VRF "default" '*' denotes best ucast next-hop '**' denotes best mcast next-hop '[x/y]' denotes [preference/metric] '%' in via output denotes VRF 2.2.2.2/32, ubest/mbest: 2/0, attached *via 2.2.2.2, Lo0, [0/0], 01:33:36, local *via 2.2.2.2, Lo0, [0/0], 01:33:36, direct 6.6.6.0/24, ubest/mbest: 1/0, attached *via 6.6.6.1, Vlan6, [0/0], 00:02:22, direct 6.6.6.1/32, ubest/mbest: 1/0, attached *via 6.6.6.1, Vlan6, [0/0], 00:02:22, local 8.8.8.0/24, ubest/mbest: 1/0 *via 6.6.6.2, Vlan6, [90/3072], 00:00:39, eigrp-1, internal ============================== Now if we add summary statement for default route under vlan 6 on Nexus 9500 : 9500 Switch : =============== 9500(config)# int vl 6 9500(config-if)# ip summary-address eigrp 1 0.0.0.0/0 250 9500(config-if)# sh run int vl 6 !Command: show running-config interface Vlan6 !Time: Wed Aug 10 03:51:12 2016 version 7.0(3)I2(1) interface Vlan6 no shutdown ip address 6.6.6.2/24 ip router eigrp 1 ip summary-address eigrp 1 0.0.0.0/0 250 9500(config-if)# sh ip route IP Route Table for VRF "default" '*' denotes best ucast next-hop '**' denotes best mcast next-hop '[x/y]' denotes [preference/metric] '%' in via output denotes VRF 0.0.0.0/0, ubest/mbest: 1/0 *via 4.4.4.1, [200/0], 00:09:38, bgp-1, internal, tag 1 4.4.4.0/24, ubest/mbest: 1/0, attached *via 4.4.4.2, Vlan4, [0/0], 00:09:38, direct 4.4.4.2/32, ubest/mbest: 1/0, attached *via 4.4.4.2, Vlan4, [0/0], 00:09:38, local 6.6.6.0/24, ubest/mbest: 1/0, attached *via 6.6.6.2, Vlan6, [0/0], 00:09:38, direct 6.6.6.2/32, ubest/mbest: 1/0, attached *via 6.6.6.2, Vlan6, [0/0], 00:09:38, local 8.8.8.0/24, ubest/mbest: 1/0, attached *via 8.8.8.2, Vlan8, [0/0], 00:09:38, direct 8.8.8.2/32, ubest/mbest: 1/0, attached *via 8.8.8.2, Vlan8, [0/0], 00:09:38, local On 9372-2 , this default route is not propagated , Also the 8.8.8.0 subnet which was advertised earlier from 9500 is no more seen . 9372-2 Switch: ================= 9372-2(config-if)# sh ip route IP Route Table for VRF "default" '*' denotes best ucast next-hop '**' denotes best mcast next-hop '[x/y]' denotes [preference/metric] '%' in via output denotes VRF 2.2.2.2/32, ubest/mbest: 2/0, attached *via 2.2.2.2, Lo0, [0/0], 01:43:05, local *via 2.2.2.2, Lo0, [0/0], 01:43:05, direct 6.6.6.0/24, ubest/mbest: 1/0, attached *via 6.6.6.1, Vlan6, [0/0], 00:11:51, direct 6.6.6.1/32, ubest/mbest: 1/0, attached *via 6.6.6.1, Vlan6, [0/0], 00:11:51, local Removing the summary command causes the 8.8.8.0 subnet to be advertised correctly in EIGRP. Also now when I add a summary route with default AD : 9500 Switch : ============= 9500(config-if)# int vl 6 9500(config-if)# ip summary-address eigrp 1 0.0.0.0/0 9500(config-if)# sh run int vl 6 !Command: show running-config interface Vlan6 !Time: Wed Aug 10 03:55:09 2016 version 7.0(3)I2(1) interface Vlan6 no shutdown ip address 6.6.6.2/24 ip router eigrp 1 ip summary-address eigrp 1 0.0.0.0/0 9500(config-if)# sh ip route IP Route Table for VRF "default" '*' denotes best ucast next-hop '**' denotes best mcast next-hop '[x/y]' denotes [preference/metric] '%' in via output denotes VRF 0.0.0.0/0, ubest/mbest: 1/0 *via Null0, [5/2816], 00:00:37, eigrp-1, discard 4.4.4.0/24, ubest/mbest: 1/0, attached *via 4.4.4.2, Vlan4, [0/0], 00:13:14, direct 4.4.4.2/32, ubest/mbest: 1/0, attached *via 4.4.4.2, Vlan4, [0/0], 00:13:14, local 6.6.6.0/24, ubest/mbest: 1/0, attached *via 6.6.6.2, Vlan6, [0/0], 00:13:14, direct 6.6.6.2/32, ubest/mbest: 1/0, attached *via 6.6.6.2, Vlan6, [0/0], 00:13:14, local 8.8.8.0/24, ubest/mbest: 1/0, attached *via 8.8.8.2, Vlan8, [0/0], 00:13:14, direct 8.8.8.2/32, ubest/mbest: 1/0, attached *via 8.8.8.2, Vlan8, [0/0], 00:13:14, local The null0 default route replaces the route learnt from BGP . Now this default route gets advertised to 9372-2 . Still 8.8.8.0 subnet that should be advertised in EIGRP from 9500 is missing. 9372 Switch : ================= 9372-2(config-if)# sh ip route IP Route Table for VRF "default" '*' denotes best ucast next-hop '**' denotes best mcast next-hop '[x/y]' denotes [preference/metric] '%' in via output denotes VRF 0.0.0.0/0, ubest/mbest: 1/0 *via 6.6.6.2, Vlan6, [90/3072], 00:02:40, eigrp-1, internal 2.2.2.2/32, ubest/mbest: 2/0, attached *via 2.2.2.2, Lo0, [0/0], 01:47:55, local *via 2.2.2.2, Lo0, [0/0], 01:47:55, direct 6.6.6.0/24, ubest/mbest: 1/0, attached *via 6.6.6.1, Vlan6, [0/0], 00:16:41, direct 6.6.6.1/32, ubest/mbest: 1/0, attached *via 6.6.6.1, Vlan6, [0/0], 00:16:41, local

Conditions

This issue is only seen for summary default routes.

Workaround

Removing eigrp default summary routes causes other EIGRP routes to be advertised correctly.

Further Problem Description