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New Member

BGP issue

Hi Guys:

We are migrating our banks sites to MPLS and having some issue

DC is the Datacenter where all the Branches will connect to access resource and reach other branches.

DRC is backup in case DC is down.

R1 is the primary router at one of the branch and R2 is secondary router which is connected to DRC (Backuplink).

We are running OSPF in the network.

Everthing is wrking fine when Dc is moved to MPLS.

But when i put R1 on MPLS i am getting loops ,if i check for routes in DC and branches i see the pathh on DC-->drc-->R2-->r1.

EBGP is running between DC and cloud ,R1 and cloud.

No BGP between R1 and R2 only OSPF.

I have tried lot of steps but not able to acheive this could any one suggest something.

Chao

Vishwa

6 REPLIES
New Member

Re: BGP issue

Hello Vishwa,

can u pls confirm which attribute value is getting from DRC router for R1.

also pls confirm that proper Local pref or weight value on DC and DRC routers for fail-over

Thanks and Regards,

Sourabh

New Member

Re: BGP issue

Hi Sourabh,

I have shut the DRC link to the MPLS,even then i am facing the issue the ,DC router itself is learning the OSPG routes that are ther in DC through

DC-->drc-->R2-->R1.

Without change

DC-Primary#sh ip route 172.16.x.x

Routing entry for 172.16.x.0/24

Known via "ospf 100", distance 110, metric 10, type extern 2, forward metric 12

Redistributing via bgp 65001

Advertised by bgp 65001 route-map BGP

Last update from 172.16.y.y on BVI10, 00:00:18 ago

Routing Descriptor Blocks:

* 172.16.x.x, from 172.16.x.x, 00:00:18 ago, via BVI10

Route metric is 10, traffic share count is 1

After Change

DC-Primary#sh ip route 172.16.x.x

Routing entry for 172.16.x.0/24

Known via "ospf 100", distance 110, metric 1

Tag 9829, type extern 2, forward metric 73

Redistributing via bgp 65001

Advertised by bgp 65001 route-map BGP

Last update from 172.16.z.z on Multilink100, 00:00:02 ago

Routing Descriptor Blocks:

* 172.16.x.x, from 172.30.x.x, 00:00:02 ago, via Multilink100

Route metric is 1, traffic share count is 1

Route tag 9829

Chao

Vishwa

Hall of Fame Super Silver

Re: BGP issue

Hello Vishwa,

you probably have multiple points of mutual redistribution, if so you need to implement forms of route filtering to avoid reinjection of routes learned from OSPF back in OSPF.

for example if routes with route tag 9829 shouldn't be advertised in BGP use

route-map OSPFtoBGP deny 10

match route-tag 9829

route-map OSPFtoBGP permit 20

router bgp xxx

red ospf process-id route-map OSPFtoBGP

A similar mirrored approach would be needed for redistribution of BGP routes into OSPF.

Also you should use OSPF external type 1 if you have multiple ASBRs in your network for routes redistributed into OSPF.

Hope to help

Giuseppe

New Member

Re: BGP issue

Hi Giuseppe ,

Thanks for the reply.

R1 and R2 are my regional office and have branches connected to it so R2 should also go to R1 and then outside through MPLS and i am only doing redistribution in R1 no BGP is running in R2 only on R1.

My doubt is will R2 prefer that route through R1 or the OSPF route through DRC.

Chao

Vishwa

Hall of Fame Super Silver

Re: BGP issue

Hello Vishwa,

to be sure a path is preferred over the other makes the primary route O E1 because O E1 route are always preferred over O E2 routes.

in your current scenario with O E2 routes the risk of suboptimal routing is high:

the route via multilink has seed metric O E2 1 < seed metric of the other route that is an O E1 10.

if they had equal values and both O E2 best forwarding metric would win.

so two options:

a) make primary route type 1

add metric-type 1 in the redistribute command

b) have an higher seed metric on backup route

using set metric 50 in the route map used in redistribution (you may need to add such a route-map on device originating secondary external route)

Edit:

the two routes are generated by two diffent routers different Router-ids see from field of the two routes

* 172.16.x.x, from 172.16.x.x, 00:00:18 ago, via BVI10

* 172.16.x.x, from 172.30.x.x, 00:00:02 ago, via Multilink100

Hope to help

Giuseppe

New Member

Re: BGP issue

Thanks Giuseppe

I have already tried route map with tags and it worked only when i shut the link from R2 to DRC,but i have not use metric type will give this a shot.

Chao

Vishwa

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