Prefer BGP over EIGRP for default route

[jay mamaradlo]

We have the task to upgrade our existing PRIMARY circuit running EIGRP over PPP DS3 to our hubsite using ethman using BGP. We have a existing Secondary ROUTER in place running EIGRP over another PPP with delay set to manage it being the secondary. I attempted to bring in the NEW Circuit using BGP and that was fine until I brought back up my Secondary. Due to EIGRP admin distance of 90, my LAN core would default to it. My preferred route it to go out my NEW ethMan Circuit using BGP. I've encountered several solutions such as 1.)Change BGP distance, 2.) Increase EIGRP delay, 3.)Summarize routes over EIGRP and use specific routes on BGP.

Is there a best practice. see attached drawing.

[Marwan ALshawi]

just to make sure i got it right

your problem is that the BGP route after being redistributed into EIGRP to the CORE the core is preferring the router over the secondary path, if ths is the case because EIGRP from the secondary path will be seen with AD 90 while the redistributed one will be seen as external route with AD 170

if this is the only external EIGRP route being received by the core what you can do it to reduce the external eigrp route AD value in the core to something less than 90

if you have other EIGRP external routes from other peers then use the summary approach where you send the more specific via the primary and a summary route via the secondary

hope this help

[jay mamaradlo]

thanks for the prompt response.

Just to clarify your statement: your problem is that the BGP route after being redistributed into EIGRP to the CORE the core is preferring the router over the secondary path,

the core is preferring the router running ONLY EIGRP which is the SECONDARY or Backup Router. I DO want it to default to the BGP Core (new PRIMARY Router) which is being redistributed in to EIGRP to my LAN Core.

Are you suggesting to REDUCE the external EIGRP Route be less than 90, shouldn't it be more than 170 which is my AD for iBGP? If so, do i do that by increasing the delay on the actual interface of the next hop interface of the Secondary Router? Would be grateful if you provided statement and to where. Thanks Again.

[Giuseppe Larosa]

Hello Jay,

playing on delay has no effect as here you have competition between EIGRP D EX external routes with EIGRP D internal routes.

As an alternative to make the  two routes comparable you can use a second EIGRP process that will run only on the secondary 45 Mbps link.

In this way redistributing EIGRP routes from process 2 to process 1 all routes will be D EX external type at this point comparison is possible and playing with delay will allow you to make the routes coming from the 45 Mbps link less preferred.

Assuming that EIGRP 100 is your main process you can use EIGRP 200 as your secondary process.

on HQ router connected  to secondary link:

router eigrp 200

default-metric 10000 10000 255 1 1500

redistribute eigrp 100 route-map HQ-ROUTES

network

!

router eigrp 100

default-metric 10000 10000 255 1 1500

redistribute eigrp 200 route-map BO-ROUTES

! all other network commands here

on Branch office router connected to secondary link:

router eigrp 200

default-metric 10000 10000 255 1 1500

redistribute eigrp 100 route-map BO-ROUTES

network

!

router eigrp 100

default-metric 10000 10000 255 1 1500

redistribute eigrp 200 route-map HQ-ROUTES

! all other network commands here

the use of the route-maps is just a safety measure and they can be used to describe the routes of each site

Hope to help

Giuseppe