Can a EIGRP route be passive with 0 successors???!

wintermute000 · April 07, 2015, 05:58:22 PM

Invesigating the world's messiest EIGRP issue (20x routers on a flat VLAN + multiple 'backdoor' links.... don't ask....)

Found strange issues with a 10.0.0.0/8 route constantly refreshing on the core and pointing to a 'stub' that isn't configured to advertise it (its not actually a EIGRP stub but logically its a stub)

On the stub I see this. Is this a flat out bug?

xxxxxxx#sh ip eigrp topology 10.0.0.0/8
EIGRP-IPv4 Topology Entry for AS(10)/ID(10.27.255.229) for 10.0.0.0/8
State is Passive, Query origin flag is 1, 0 Successor(s), FD is Infinity
Descriptor Blocks:
xxxxxxx#

Whats worse is that on the core, its installing this route in the RiB, even though it says clearly the route is active (and this 'stub' is replying with infinite metric)

CORExxx#sh ip eigrp topology active
EIGRP-IPv4 Topology Table for AS(10)/ID(10.27.255.254)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status

A 10.0.0.0/8, 1 Successors, FD is 5560320
1 replies, active 00:00:30, query-origin: Local origin
via 10.27.252.219 (Infinity/Infinity), Vlan287, serno 2669168
via 10.27.254.233 (Infinity/Infinity), Vlan1, serno 2669177
via 10.27.254.231 (Infinity/Infinity), Vlan1, serno 2669176
via 10.27.254.232 (Infinity/Infinity), Vlan1, serno 2669175
via 10.27.254.229 (Infinity/Infinity), Vlan1, serno 2669174
via 10.27.253.225 (Infinity/Infinity), Vlan274, serno 2669173
via 10.27.253.241 (Infinity/Infinity), Vlan275, serno 2669172
via 10.27.254.220 (Infinity/Infinity), Vlan1, serno 2669171
via 10.30.255.25 (Infinity/Infinity), TenGigabitEthernet2/9/8, serno 2669170
via 10.30.255.17 (Infinity/Infinity), r, TenGigabitEthernet1/9/8, serno 2669169
via Rstatic (Infinity/Infinity)

CORExxx#sh ip route 10.0.0.0 255.0.0.0
Routing entry for 10.0.0.0/8
Known via "eigrp 10", distance 90, metric 5560320, type internal
Redistributing via eigrp 10, bgp 65002
Last update from 10.27.252.219 on Vlan287, 00:00:36 ago
Routing Descriptor Blocks:
* 10.27.252.219, from 10.27.252.219, 00:00:36 ago, via Vlan287
Route metric is 5560320, traffic share count is 1
Total delay is 119550 microseconds, minimum bandwidth is 1024 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 255/255, Hops 2

javentre · April 07, 2015, 06:47:30 PM

Quote from: wintermute000 on April 07, 2015, 05:58:22 PMFound strange issues with a 10.0.0.0/8 route constantly refreshing on the core and pointing to a 'stub' that isn't configured to advertise it (its not actually a EIGRP stub but logically its a stub)

How is it not "configured to advertise it"? Is it filtered with a distribute list or prefix list?

Unless you've made it an actual eigrp stub, anything it learns out one interface may be eligible to be advertised out another interface - it can be a transit.

The FD set to infinity just means it has a better source for the route, like another protocol with a better AD.

Please post the sh ip route xxxx and EIGRP topo from both the core and your device that you call a sub - which isn't an actual stub. Please keep the hostnames (or whatever you want to sanitize them to) in each output so it's clear where it came from.

wintermute000 · April 07, 2015, 08:48:46 PM

by that I mean there are no other routers in the network originating 10/8. If the router that is originating it thinks the next hop is somewhere else, then we have a routing loop?

Observe, doesn't make sense - according to EIGRP the core router should be seeing this route as active and has no EIGRP route with anything except infinite metric, yet it happily installs a route to the above 3945

CORE#sh ip route 10.0.0.0 255.0.0.0
Routing entry for 10.0.0.0/8
Known via "eigrp 10", distance 90, metric 5560320, type internal
Redistributing via eigrp 10, bgp 65002
Last update from 10.27.252.219 on Vlan287, 00:00:39 ago
Routing Descriptor Blocks:
* 10.27.252.219, from 10.27.252.219, 00:00:39 ago, via Vlan287
Route metric is 5560320, traffic share count is 1
Total delay is 119550 microseconds, minimum bandwidth is 1024 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 255/255, Hops 2

CORE#sh ip eigrp topology 10.0.0.0 255.0.0.0
EIGRP-IPv4 Topology Entry for AS(10)/ID(10.27.255.254) for 10.0.0.0/8
State is Active, Query origin flag is 1, 1 Successor(s), FD is 5560320
Waiting for 1 replies
Descriptor Blocks:
10.27.252.219 (Vlan287), from 10.27.252.219, Send flag is 0x0
Composite metric is (4294967295/4294967295), route is Internal
Vector metric:
Minimum bandwidth is 1024 Kbit
Total delay is 167772159 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 0
10.27.254.231 (Vlan1), from 10.27.254.231, Send flag is 0x0
Composite metric is (4294967295/4294967295), route is Internal
Vector metric:
Minimum bandwidth is 1024 Kbit
Total delay is 167772159 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 0
10.27.254.233 (Vlan1), from 10.27.254.233, Send flag is 0x0
Composite metric is (4294967295/4294967295), route is Internal
Vector metric:
Minimum bandwidth is 1024 Kbit
Total delay is 167772159 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 0
10.27.254.232 (Vlan1), from 10.27.254.232, Send flag is 0x0
Composite metric is (4294967295/4294967295), route is Internal
Vector metric:
Minimum bandwidth is 1024 Kbit
Total delay is 167772159 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 0
10.27.254.229 (Vlan1), from 10.27.254.229, Send flag is 0x0
Composite metric is (4294967295/4294967295), route is Internal
Vector metric:
Minimum bandwidth is 1024 Kbit
Total delay is 167772159 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 0
10.27.253.225 (Vlan274), from 10.27.253.225, Send flag is 0x0
Composite metric is (4294967295/4294967295), route is Internal
Vector metric:
Minimum bandwidth is 1024 Kbit
Total delay is 167772159 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 0
Originating router is 10.27.255.254
10.27.253.241 (Vlan275), from 10.27.253.241, Send flag is 0x0
Composite metric is (4294967295/4294967295), route is Internal
Vector metric:
Minimum bandwidth is 1024 Kbit
Total delay is 167772159 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 0

CORE# show ip eigrp topology active
EIGRP-IPv4 Topology Table for AS(10)/ID(10.27.255.254)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status

A 10.0.0.0/8, 1 Successors, FD is 5560320
1 replies, active 00:00:28, query-origin: Local origin
via 10.27.252.219 (Infinity/Infinity), Vlan287, serno 2670897
via 10.27.254.233 (Infinity/Infinity), Vlan1, serno 2670905
via 10.27.254.231 (Infinity/Infinity), Vlan1, serno 2670904
via 10.27.254.229 (Infinity/Infinity), Vlan1, serno 2670903
via 10.27.254.232 (Infinity/Infinity), Vlan1, serno 2670902
via 10.27.254.220 (Infinity/Infinity), Vlan1, serno 2670901
via 10.27.253.225 (Infinity/Infinity), Vlan274, serno 2670900
via 10.30.255.25 (Infinity/Infinity), TenGigabitEthernet2/9/8, serno 2670899
via 10.27.253.241 (Infinity/Infinity), Vlan275, serno 2670898
via 10.30.255.17 (Infinity/Infinity), r, TenGigabitEthernet1/9/8, serno 2670896
via Rstatic (Infinity/Infinity)

javentre · April 08, 2015, 06:06:11 AM

What's your redistribution configuration?

that1guy15 · April 08, 2015, 11:01:33 AM

smells like auto-summary to me.

Im on the road so I cant dig into your output much.

wintermute000 · April 09, 2015, 05:44:26 AM

yeah we though of that, but it wasn't it....

got to the bottom of the issue anyway, though apparently according to one of my colleagues its basically like a RiB fail i.e. there is a better AD route. He mocked it up with a static route to illustrate (he also has the magic digits so I'll take his word for it!)

dlots · April 16, 2015, 02:25:59 PM

I assume you have clear EIGRP neighbors?
You might try shutting down EIGRP and restarting it on that stub.
What does the sub router show when you do a show ip route 10.0.0.0, if it's not showing as connected making that router a stub should fix the issue, or at the very least get everything working till you can figure out where that 10.0.0.0/8 is coming from and how to kill it.

wintermute000 · April 27, 2015, 05:45:09 PM

nah its all good, customer had a stupid design.

- redist static route with AD200 into EIGRP
- neighbor router has two L3 links back for redundancy I guess, offset list on one
- EIGRP redist to neighbor
- neighbor has offset list so no split horizon and sends EIGRP route back to originating router
- originating router's route is AD200 so EIGRP wins
- cascading chain of queries and poison reverses as there are 20 (!!!) EIGRP neighbors adjacent on that VLAN
- originating router withdraws static route from RiB
- no EIGRP route to redist
- EIGRP route wishdrawn on neighbor
- repeat ad infinitum