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vpnv4 routes on TE-Tunnel down

friends,

 

i have redundant links between two MPLS PE routers with MPLS enabled on one link only.  OSPF is enabled on both links.   I am using TE Tunnels to forward VPN traffic between PE.  

                     
CE1 ---ebgp----PE1 ======mpBGP======= PE2 ------ebgp---CE2

 

The problem i am facing is that when MPLS Link goes down it results in MPLS-TE Tunnel to go down, however since iBGP remain established via secondary link, VPNv4 routes are received at both end and further advertised to CE routers, but these routes are useless for CE as MPLS is down in ISP Core. 

Is there anyway to suppress vpnv4 routes when MPLS TE Tunnel goes down??

 

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Accepted Solutions
Cisco Employee

Hi,Is there any specific

Hi,

Is there any specific design reason for not enabling/utilizing the redundant link with mpls enabled?. 

 

When you say mpls link goes down, Am I assuming right that the egress interface (on which you have mpls enabled) goes down?. You can use this interface as update-source in your bgp session (towards remote PE). So if the link goes down, the session will also come down and no vpnv4 updates will be sent to CE.

 

3 REPLIES
Cisco Employee

Hi,Is there any specific

Hi,

Is there any specific design reason for not enabling/utilizing the redundant link with mpls enabled?. 

 

When you say mpls link goes down, Am I assuming right that the egress interface (on which you have mpls enabled) goes down?. You can use this interface as update-source in your bgp session (towards remote PE). So if the link goes down, the session will also come down and no vpnv4 updates will be sent to CE.

 

New Member

Well the reason for not

Well the reason for not enabling MPLS on other link is the limitation of MTU on it.. MPLS will not work porperly... But since its good enough for data traffic... We have enabled OSPF on it.

update source we use for iBGP is the loopbacks. and we have to use loopbacks because of many other PEs in network having connectivity with it... So even if mpls link goes down... loopbacks are reachable via other link causing BGP session to stay up.

any solution for this design?

 

Cisco Employee

If the update source is

If the update source is reachable via other non-mpls link, it may not help. Depending on what version you run, yu might try vrf aware bgp conditional advertisement,

http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/configuration/xe-3s/irg-xe-3s-book/irg-vrf-conditional-adv.pdf

 

If your IOS version doesnt support the above feature, the otehr option I can think of  is to use Object tracking to track the TE tunnel interface (line protocol) and use the down state as event for EEM applet. Configure the action to execute a CLI to filter all prefixes to your CE. 

 

You may need another EEM script tracking the UP state of track and execute CLI as action to remove teh filter.

 

-Nagendra

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