Re: EIGRP flushing default route - Page 2

Daniel Freitas · ‎09-28-2017

Hi for all!

I have a weird scenario on my network. I have a Cat 6880 as a core of a site. This switch is connected to two 2921 that are connected with two different MPLS providers. On the border routers I'm injecting the full routing table of the site to the MPLS and injecting back on the EIGRP just the default route. The main issue that I am facing on this scenario is that when one provider comes down, on the core of the network both default routes are reset and I face some minutes outage until the network is able to re-converge. Any thoughts why this is happening?

Thanks in advance,

Daniel Freitas

CCIE SP

Daniel Freitas · ‎09-28-2017

Your assumption is correct.

In the Data Center site (not the one where I'm facing the issue) there is a static route to a FW, and this static is injected on the BGP trough redistribution, with the following sequence:

ip route 0.0.0.0 0.0.0.0 10.55.48.113

router bgp 65000
bgp log-neighbor-changes

redistribute static route-map STATIC_to_BGP

<<<<<<<<<<<<<<<<<<<<<OUTPUT OMMITED>>>>>>>>>>>>>>>>>>>

default-information originate

route-map STATIC_to_BGP permit 10
match ip address prefix-list STATIC_to_BGP

ip prefix-list STATIC_to_BGP seq 5 permit 0.0.0.0/0

<<<<<<<<<<<<<<<<<<<<<OUTPUT OMMITED>>>>>>>>>>>>>>>>>>>

chrihussey · ‎09-28-2017

Ok, so this site recieves the default route from BGP and redistributes it into EIGRP.

Could you post the output of "show ip route 0.0.0.0" and "show ip eigrp topology" from both 2921 routers in normal operation mode?

Daniel Freitas · ‎09-28-2017

BR06-RT-MPLS-01#sh ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
Known via "bgp 65006", distance 20, metric 0, candidate default path
Tag 18881, type external
Redistributing via eigrp 65006
Advertised by eigrp 65006 route-map BGP-to-EIGRP_GVT
Last update from 10.55.48.69 1w3d ago
Routing Descriptor Blocks:
* 10.55.48.69, from 10.55.48.69, 1w3d ago
      Route metric is 0, traffic share count is 1
      AS Hops 3
      Route tag 18881
      MPLS label: none
BR06-RT-MPLS-01#sh ip eigrp topo
EIGRP-IPv4 VR(LOGICALIS) Topology Table for AS(65006)/ID(10.55.43.51)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
       r - reply Status, s - sia Status

P 10.55.46.32/27, 1 successors, FD is 1982464
        via 10.55.43.38 (1982464/1327104), Port-channel1
P 10.55.43.52/32, 1 successors, FD is 2048000
        via 10.55.43.38 (2048000/1392640), Port-channel1
P 10.55.34.0/24, 1 successors, FD is 1982464
        via 10.55.43.38 (1982464/1327104), Port-channel1
P 10.55.46.100/32, 1 successors, FD is 163840
        via Connected, Loopback1
P 10.55.46.97/32, 1 successors, FD is 1392640
        via 10.55.43.38 (1392640/163840), Port-channel1
P 10.55.38.0/26, 1 successors, FD is 1982464
        via 10.55.43.38 (1982464/1327104), Port-channel1
P 10.55.38.64/26, 1 successors, FD is 1982464
        via 10.55.43.38 (1982464/1327104), Port-channel1
P 10.55.38.192/26, 1 successors, FD is 1982464
        via 10.55.43.38 (1982464/1327104), Port-channel1
P 10.55.43.64/27, 1 successors, FD is 1982464
        via 10.55.43.38 (1982464/1327104), Port-channel1
P 10.55.43.96/27, 1 successors, FD is 1982464
        via 10.55.43.38 (1982464/1327104), Port-channel1
P 10.55.42.0/24, 1 successors, FD is 1982464
        via 10.55.43.38 (1982464/1327104), Port-channel1
P 10.55.43.44/30, 1 successors, FD is 1327104
        via 10.55.43.38 (1327104/32768), Port-channel1
P 10.55.43.0/27, 1 successors, FD is 1982464
        via 10.55.43.38 (1982464/1327104), Port-channel1
P 10.55.32.0/24, 1 successors, FD is 1982464
        via 10.55.43.38 (1982464/1327104), Port-channel1
P 10.55.40.0/24, 1 successors, FD is 1982464
        via 10.55.43.38 (1982464/1327104), Port-channel1
P 10.55.43.40/30, 1 successors, FD is 1966080
        via 10.55.43.38 (1966080/1310720), Port-channel1
P 10.55.26.64/26, 1 successors, FD is 1982464
        via 10.55.43.38 (1982464/1327104), Port-channel1
P 10.55.48.68/30, 1 successors, FD is 13107200
        via Connected, GigabitEthernet0/2
P 10.55.25.80/28, 1 successors, FD is 1982464
        via 10.55.43.38 (1982464/1327104), Port-channel1
P 10.55.47.128/27, 1 successors, FD is 1982464
        via 10.55.43.38 (1982464/1327104), Port-channel1
P 10.55.25.16/28, 1 successors, FD is 1982464
        via 10.55.43.38 (1982464/1327104), Port-channel1
P 0.0.0.0/0, 1 successors, FD is 1310720, tag is 18881
        via Redistributed (1310720/0)
P 10.55.26.192/26, 1 successors, FD is 1982464
        via 10.55.43.38 (1982464/1327104), Port-channel1
P 10.55.41.0/24, 1 successors, FD is 1982464
        via 10.55.43.38 (1982464/1327104), Port-channel1
P 10.55.46.101/32, 1 successors, FD is 2048000
        via 10.55.43.38 (2048000/1392640), Port-channel1
P 10.55.43.56/30, 1 successors, FD is 1327104
        via 10.55.43.38 (1327104/32768), Port-channel1
P 10.55.43.32/30, 1 successors, FD is 1327104
        via 10.55.43.38 (1327104/32768), Port-channel1
P 10.55.43.36/30, 1 successors, FD is 1310720
        via Connected, Port-channel1
P 10.55.33.0/24, 1 successors, FD is 1982464
        via 10.55.43.38 (1982464/1327104), Port-channel1
P 10.55.46.64/27, 1 successors, FD is 1982464
        via 10.55.43.38 (1982464/1327104), Port-channel1
P 10.55.43.51/32, 1 successors, FD is 163840
        via Connected, Loopback0
P 10.55.38.128/27, 1 successors, FD is 1982464
        via 10.55.43.38 (1982464/1327104), Port-channel1

============================================================

BR06-RT-MPLS-02#sh ip route 0.0.0.0
Routing entry for 0.0.0.0/0, supernet
Known via "bgp 65006", distance 20, metric 0, candidate default path
Tag 64517, type external
Redistributing via eigrp 65006
Advertised by eigrp 65006 route-map BGP-to-EIGRP_EBT
Last update from 189.42.183.61 2d01h ago
Routing Descriptor Blocks:
* 189.42.183.61, from 189.42.183.61, 2d01h ago
      Route metric is 0, traffic share count is 1
      AS Hops 4
      Route tag 64517
      MPLS label: none
BR06-RT-MPLS-02#sh ip eigrp topo
EIGRP-IPv4 VR(LOGICALIS) Topology Table for AS(65006)/ID(10.55.43.52)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
       r - reply Status, s - sia Status

P 10.55.46.32/27, 1 successors, FD is 1982464
        via 10.55.43.42 (1982464/1327104), Port-channel2
P 10.55.43.52/32, 1 successors, FD is 163840
        via Connected, Loopback0
P 10.55.34.0/24, 1 successors, FD is 1982464
        via 10.55.43.42 (1982464/1327104), Port-channel2
P 10.55.46.100/32, 1 successors, FD is 2048000
        via 10.55.43.42 (2048000/1392640), Port-channel2
P 10.55.46.97/32, 1 successors, FD is 1392640
        via 10.55.43.42 (1392640/163840), Port-channel2
P 10.55.38.0/26, 1 successors, FD is 1982464
        via 10.55.43.42 (1982464/1327104), Port-channel2
P 10.55.38.64/26, 1 successors, FD is 1982464
        via 10.55.43.42 (1982464/1327104), Port-channel2
P 10.55.38.192/26, 1 successors, FD is 1982464
        via 10.55.43.42 (1982464/1327104), Port-channel2
P 10.55.43.64/27, 1 successors, FD is 1982464
        via 10.55.43.42 (1982464/1327104), Port-channel2
P 10.55.43.96/27, 1 successors, FD is 1982464
        via 10.55.43.42 (1982464/1327104), Port-channel2
P 10.55.42.0/24, 1 successors, FD is 1982464
        via 10.55.43.42 (1982464/1327104), Port-channel2
P 10.55.43.44/30, 1 successors, FD is 1327104
        via 10.55.43.42 (1327104/32768), Port-channel2
P 10.55.43.0/27, 1 successors, FD is 1982464
        via 10.55.43.42 (1982464/1327104), Port-channel2
P 10.55.32.0/24, 1 successors, FD is 1982464
        via 10.55.43.42 (1982464/1327104), Port-channel2
P 10.55.40.0/24, 1 successors, FD is 1982464
        via 10.55.43.42 (1982464/1327104), Port-channel2
P 10.55.43.40/30, 1 successors, FD is 1310720
        via Connected, Port-channel2
P 10.55.26.64/26, 1 successors, FD is 1982464
        via 10.55.43.42 (1982464/1327104), Port-channel2
P 10.55.48.68/30, 1 successors, FD is 14417920
        via 10.55.43.42 (14417920/13762560), Port-channel2
P 10.55.25.80/28, 1 successors, FD is 1982464
        via 10.55.43.42 (1982464/1327104), Port-channel2
P 10.55.47.128/27, 1 successors, FD is 1982464
        via 10.55.43.42 (1982464/1327104), Port-channel2
P 10.55.25.16/28, 1 successors, FD is 1982464
        via 10.55.43.42 (1982464/1327104), Port-channel2
P 0.0.0.0/0, 1 successors, FD is 1310720, tag is 64517
        via Redistributed (1310720/0)
P 10.55.26.192/26, 1 successors, FD is 1982464
        via 10.55.43.42 (1982464/1327104), Port-channel2
P 10.55.41.0/24, 1 successors, FD is 1982464
        via 10.55.43.42 (1982464/1327104), Port-channel2
P 10.55.46.101/32, 1 successors, FD is 163840
        via Connected, Loopback1
P 10.55.43.56/30, 1 successors, FD is 1327104
        via 10.55.43.42 (1327104/32768), Port-channel2
P 10.55.43.32/30, 1 successors, FD is 1327104
        via 10.55.43.42 (1327104/32768), Port-channel2
P 10.55.43.36/30, 1 successors, FD is 1966080
        via 10.55.43.42 (1966080/1310720), Port-channel2
P 10.55.33.0/24, 1 successors, FD is 1982464
        via 10.55.43.42 (1982464/1327104), Port-channel2
P 10.55.46.64/27, 1 successors, FD is 1982464
        via 10.55.43.42 (1982464/1327104), Port-channel2
P 10.55.43.51/32, 1 successors, FD is 2048000
        via 10.55.43.42 (2048000/1392640), Port-channel2
P 10.55.38.128/27, 1 successors, FD is 1982464
        via 10.55.43.42 (1982464/1327104), Port-channel2

chrihussey · ‎09-29-2017

Thank you.

From a configuration perspective there does not appear to be anything wrong. Looks pretty solid. I really think the problem may not necessarily be at this site, but more of the time for the routing changes to propogate across the MPLS cloud when one of the ISPs goes down.

I can't explain why the default route shows the same uptime and seems to reset when this happens, nor can I test it out, but it may simply be part of the EIGRP recalculation when this occurs. In other words, more cosmetic than the issue.

The best course of action may be to schedule a test in a maintenance window, fail the connection to ISP 1 and see what happens to the default route as well as the routing at both this site and the data center. I think that should at the very least provide some answers on where to focus to resolve this issue.

Julio E. Moisa · ‎09-29-2017

Hi

Currently the next hop is through MPLS2, It is a very weird situation but as mentioned Chrihussey it can be cosmetic trouble, also apparently the core is receiving the default route with the same metric from both Edge Routers.

D*EX 0.0.0.0/0 [170/15360] via 10.55.43.41, 1d21h, TenGigabitEthernet2/1/1
[170/15360] via 10.55.43.37, 1d21h, TenGigabitEthernet1/1/1

Is possible to have the configuration regarding this issue, EIGRP, BGP an static routes from each one. Other way is and as it was mentioned previously create an authorized maintenance window and shutdown the primary (also you should see if it is the same behavior with MPLS2). The route on R2 should be advertised via redistribution with higher metric that the received from R1

>> Marcar como útil o contestado, si la respuesta resolvió la duda, esto ayuda a futuras consultas de otros miembros de la comunidad. <<

Daniel Freitas · ‎10-02-2017

I will perform a maintenance window in the next weekend to perform a proper troubleshooting. Any advice about debugging that I should run during the window?

Julio E. Moisa · ‎10-02-2017

Hi

You could execute: debug ip eigrp <ID> 0.0.0.0 0.0.0.0

Also check the EIGRP topology during the window.

Please keep us posted.

>> Marcar como útil o contestado, si la respuesta resolvió la duda, esto ayuda a futuras consultas de otros miembros de la comunidad. <<

Daniel Freitas · ‎10-06-2017

I will perform the maintenace window on the next Thursday.

I let you guys know about the result.

Thanks for all so far!

chrihussey · ‎10-13-2017

Just checking in. Were you able to test?