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Why host routes are injected on routers forming MP-BGP eBGP peers on VPNv4

Hi experts,

 

I was studying on my lab rack and I was actually playing with DMVPN but suddenly decided to try eBGP peering on VPNv4. I have two DMVPN hubs (R1 and R2) and one spoke (R11). I used dual-home single-VPN design so all the tunnels are in the same subnet 192.168.12.0/24. The devices are having .1, .2 and .11 respectively.

 

Then I was building BGP peering on the 192.168.12.0/24 subnet. Here is when I found something very interesting. As soon as the VPNv4 peering established, the routers would add a /32 host route of the peer and it is shown as "connected" type.

 

R1(config-router)#do sh ip route 192.168.12.11

Routing entry for 192.168.12.11/32

  Known via "connected", distance 0, metric 0 (connected, via interface)

  Redistributing via eigrp 100

  Advertised by eigrp 100

  Routing Descriptor Blocks:

  * directly connected, via Tunnel0

      Route metric is 0, traffic share count is 1

 

R11#sho ip route 192.168.12.1

Routing entry for 192.168.12.1/32

  Known via "connected", distance 0, metric 0 (connected, via interface)

  Redistributing via eigrp 100

  Advertised by eigrp 100

  Routing Descriptor Blocks:

  * directly connected, via Tunnel12

      Route metric is 0, traffic share count is 1

 

Before it was established, it is shown correctly as the /24 route

 

R1#sh ip route 192.168.12.11

Routing entry for 192.168.12.0/24

  Known via "connected", distance 0, metric 0 (connected, via interface)

  Redistributing via eigrp 100

  Routing Descriptor Blocks:

  * directly connected, via Tunnel0

      Route metric is 0, traffic share count is 1

 

Here is with debug. As you can see the route is injected as soon as the peering is formed

 

*Jun 19 20:43:23.539: %BGP-5-ADJCHANGE: neighbor 192.168.12.11 Up

R1(config-router-af)#

*Jun 19 20:43:23.540: RT: updating connected 192.168.12.11/32 (0x0):

    via 0.0.0.0 Tu0

 

*Jun 19 20:43:23.540: RT: add 192.168.12.11/32 via 0.0.0.0, connected metric [0/0]

*Jun 19 20:43:23.566: RT: updating eigrp 192.168.12.1/32 (0x0):

    via 192.168.12.11 Tu0

 

*Jun 19 20:43:23.566: RT: rib update return code: 17

 

Any ideas? Thanks!

1 REPLY
New Member

It apparently not specific to

It apparently not specific to the DMVPN setup. I have tried building BGP peering between routers on ethernet on vpnv4 address family, and the host route is added as well. Any ideas?

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