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aravinda099
Beginner

BGP - Route advertising

I have two routers that has a static route configured for the LAN side which re-distributes via BGP to the WAN.

One of the routers does not have anything connected to LAN subnet/ interface. Other one is live.

Will this create a routing conflict in the network ?

7 REPLIES 7
daniel.dib
Rising star

Can you draw a topology? Are you saying both routers redistribute it via BGP but only one of them can actually reach that network? In that case there could be a black hole issue if traffic arrives on the "wrong" router.

Daniel Dib
CCIE #37149

Daniel Dib
CCIE #37149
CCDE #20160011

Please rate helpful posts.

This was tested and it is working as expected. 

Can configure the same LAN and have static route configured. As long as they both aren't active at the same time. 

AhmedMusa
Beginner

Yes, there is an issue here.

why the secondary router is advertising the LAN routes while it doesn't have reachabiility to the LAN.

In case if you are planning to connect the LAN lter it is recomended to configure the static routes with the exit interface.

i.e Ip route x.x.x.x y.y.y.y [LAN interface] [next hop ip add]

Ahmed

@ Daniel - I will post a topolgy diagram soon.

@ Ahmed - The circuits being built side by side and turn old one off and use the new one. Same LAN used to minimize interruptions / downtime . So if the next hop is configured as the interface ID not the IP address, it won't cause a routing conflict ?

veneet.thakur
Beginner

Hi Arvind,

Are these two routers a part of LAN topology? If so then we can enable IBGP between them to resolve the routing issues.

A topology diagram will help in detail understanding, thanks.


Sent from Cisco Technical Support Android App

tudor dan
Beginner

Hi,

If the next hop is not reachable, then the static route won't be kept in the routing table, meaning it won't be advertised by that router. IBGP between them would fix the problem.

Regards,

Tudor

paul driver
VIP Mentor

Hello

If nothing is connected to it and your advertsieng that a static through that interface which doesnt dosnt go anywhere then you could blackhole traffic !

I would sugggest take the static out if its not being used, no need to have ghost config when its isnt required.

 

res

Paul



kind regards
Paul

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