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New Member

sub interface inter-as option B?

two as, as 1 and as 2,want to connect through GE interface,GSR platform.

we want to use option B, but AS 1 internet routing is running in a vpn. global routing is private address.

i want to use two sub interfae on GE, one interface connect mpls vpn option B ,global routing for two as,one subinterfae connect AS 1 internet vpn to as 2 global routing.

can i config mpls inter-as optin B under sub interface. is there any problem, and another sub interfae as vrf interface.

thank you!

tom

6 REPLIES
Cisco Employee

Re: sub interface inter-as option B?

Hi Tom,

What is the final goal of this interconnection?

1. Provide internet access to AS2 through AS1 ?

2. Exchange mpls/vpn's routing information between the 2 ASs ?

If you are interested just in 1) I think connecting AS1(vrf)---AS2(global) should be enough. Basically, AS2 becomes a client/CE of AS1.

Rgds,

Daniel

New Member

Re: sub interface inter-as option B?

Hi Daniel,

Thank you!

this is a temporary stage during migrate process .

we have two AS which are two independent AS, Each has exit point to internet, we want to merge AS2 to AS1, and remove AS2 completely at last.

but internet is running in a VPN in AS2,global routing in AS2 is private address space. we want to establish a MP-EBGP,global routing neighbor , and exchange routing information in internet vpn in AS2 and internet routing within AS1 global routing.

so we want to use inter-as optin B,but we just have one GE interface,so we will create two sub interface, one for MP-EBGP,exchange mpls vpn routing and global routing(this is a lable interface,exchange vpn lable), one for AS2 internet vpn connect to AS1 global routing(this is vrf interface pure IP).

does MP-EBGP support run on sub interfae for GE interface,can we exchange lable informaion and lable forwarding on this sub interface.

we don't exchange full internet routing table ,just local AS and default routing.

another option is that we put mp-ebgp ,lable interface under physical interface. and internet vpn under sub interface.

thank you!

Tom

Cisco Employee

Re: sub interface inter-as option B?

Hi Tom,

To answer you question, yes you can configure MP_eBGP over a subinterface, provided you have the right IOS version and HW. Check the following url for more details,

http://www.cisco.com/en/US/docs/ios/12_0s/feature/guide/fsiasmlp.html

However, IMO you really don't need this. The way I would do do it is, have the internet vrf in AS2 to connected directly to the global routing table of AS1 (either over a subinterface or main interface). Additionally, if you need to have visibility of AS1 GRT, for example for management purposes, you could add a subinterface connecting AS1 and AS2 global routing tables, in this case you could run eBGP + label if you require to have continuos LSPs between the two ASs.

Rgds,

Daniel

Hall of Fame Super Silver

Re: sub interface inter-as option B?

Hello Tom,

this is possible but depending on number of VPNv4 routes exchanged and number of Internet routes you can face problems with the CEF table sizes at the linecard level.

You may need a powerful linecard engine5 for signalling plane scalability.

Hope to help

Giuseppe

New Member

Re: sub interface inter-as option B?

Hi,Giuseppe,

thank you!

we just exhange local AS routing and default routing.

vpn routes we will check.

we don't have engine 5 line card ,just engine2 or engine3 ,is there any problem

can i config poliy routing on engine 2 or engine 3?

thank you!

Tom

Hall of Fame Super Silver

Re: sub interface inter-as option B?

Hello Tom,

if so you shouldn't have scalability issues on the control plane.

>> can i config poliy routing on engine 2 or engine 3?

You might not be able to configure it on Engine2 linecard (very likely I remember another thread about this) you may be able to configure PBR in Engine3.

Hope to help

Giuseppe

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