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VSP OSPF with fabric SPBM/ISIS

  • 1 December 2020
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Hi,

Apologies if this is a simple question.

Have a S8 network that is being migrated to VSP’s. The legacy network predominantly uses OSPF.

The question I have is with the new network built on SPBM / IS-IS fabric using GRT (IP Shortcuts). That means I will be running both IS-IS and OSPF.

As networks that are transitioned to the VSP on the GRT will use IS-IS of which redistribution of directly connected networks will be applied to the router isis.

OSPF will also be enabled, but predominantly for external routing devices to interact with the new.

That means I essentially need to redistribute directly connected networks in IS-IS into OSPF, and OSPF learned routes into IS-IS, but obviously stop a routing loop between the two i.e. possibly need to create a route map to achieve this?

Now that might be the right or wrong way of doing it, even could possibly have my understanding wrong.

Either way I’m looking for some guidance on the best practice and what the config might look like to achieve this.

Many thanks in advance.

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Best answer by Miguel-Angel RODRIGUEZ-GARCIA 1 December 2020, 13:34

Martin,

 

A route-map is not really necessary, you’ll have to play with the route redistribution rules.

Depending on where is located your default route, you could redistribute OSPF in ISIS and ISIS in OSPF or not. Those rules are of course VRF dependent

Here an example of redistribute rules I use between OSPF and ISIS:

#

# IP REDISTRIBUTION CONFIGURATION - GlobalRouter

#

router ospf

redistribute isis

redistribute static

redistribute static enable

exit

router isis

redistribute static

redistribute static metric 1

redistribute static enable

redistribute direct

redistribute direct route-map "deny-vist-address"

redistribute direct enable

exit

ip ospf apply redistribute static

isis apply redistribute static

isis apply redistribute direct

Mig

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Userlevel 6
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Martin,

 

A route-map is not really necessary, you’ll have to play with the route redistribution rules.

Depending on where is located your default route, you could redistribute OSPF in ISIS and ISIS in OSPF or not. Those rules are of course VRF dependent

Here an example of redistribute rules I use between OSPF and ISIS:

#

# IP REDISTRIBUTION CONFIGURATION - GlobalRouter

#

router ospf

redistribute isis

redistribute static

redistribute static enable

exit

router isis

redistribute static

redistribute static metric 1

redistribute static enable

redistribute direct

redistribute direct route-map "deny-vist-address"

redistribute direct enable

exit

ip ospf apply redistribute static

isis apply redistribute static

isis apply redistribute direct

Mig

Userlevel 6
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Thanks Mig, really appreciated.

Cheers,

Martin

Userlevel 1

Here is another example.

I do this to stop the routing loops occurring between OSPF and ISIS. Should be able to use this config universally on any pair of switches doing redistribution (diagram attached). You would do this on both peer switches.


(config)#route-map "peer-block-external" 1
(route-map)#no permit
(route-map)#enable
(route-map)#match metric-type-isis external
(route-map)#exit

(config)#route-map "peer-block-external-ospf" 1
(route-map)#no permit
(route-map)#enable
(route-map)#match route-type external-2
(route-map)#exit

(config)#router isis
(config-isis)#redistribute ospf
(config-isis)#redistribute ospf metric-type external
(config-isis)#redistribute ospf enable
(config-isis)#redistribute direct
(config-isis)#redistribute direct enable
(config-isis)#accept adv-rtr x.x.x.x (peer spb nickname)
(config-isis)#accept adv-rtr x.x.x.x route-map "peer-block-external"
(config-isis)#accept adv-rtr x.x.x.x enable
(config-isis)#exit
(config)#isis apply redistribute ospf
(config)#isis apply redistribute direct
(config)#isis apply accept

(config)# router ospf
(config-ospf)# router-id x.x.x.x
(config-ospf)# as-boundary-router enable
(config-ospf)# redistribute isis
(config-ospf)# redistribute isis enable
(config-ospf)# redistribute direct
(config-ospf)# redistribute direct enable
(config-ospf)# redistribute static (if static routes exist)
(config-ospf)# redistribute static enable (if static routes exist)
(config-ospf)#accept adv-rtr x.x.x.x (Peer router ID) enable
(config-ospf)#accept adv-rtr x.x.x.x route-map peer-block-external-ospf
(config-ospf)# exit
(config)#router ospf enable
(config)#ip ospf apply redistribute isis
(config)#ip ospf apply redistribute direct
(config)#ip ospf apply redistribute static (if static routes exist)
(config)#ip ospf apply accept

 

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Thanks,  that’s perfect.

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