Hi All,
I have a few Q’s about BGP/MPLS/VPN that I haven’t found answer on, on any text or community. As they are all related, I think it's better to open a single thread for them all.
1- consider this setup on PE1 - PE2 (the objective here is for PE1 and PE2 to see all each other's routes for a specific VRF):
PE1
ip vrf lab
rd 100:1
route-target export 100:2
route-target import 100:3
PE2
ip vrf lab
rd 100:1
route-target export 100:3
route-target import 100:2
This should work fine, because RD, RT-IMP and RT-EXP (on each single router) are totally unrelated; am I correct? (As long as the statements cross-match with the other router of course)
2- focusing on how a single PE advertises routes into MPBGP,
PE1
ip vrf lab
rd 100:1
export map VPN-A
route-target export 100:2
route-target import 100:3
route-map VPN-A permit 10
set extcommunity rt 100:5
The effect should be: PE1 advertises all its routes into MPBGP, with just one RT-EXP value (that is 5); is that right?
So for ex., this PE2 should be able to import all those routes:
PE2
ip vrf lab
rd 100:1
route-target export 100:3
route-target import 100:5
And this PE3 shouldn't be able to import any routes from PE1, right?
PE2
ip vrf lab
rd 100:1
route-target export 100:3
route-target import 100:2
Basically this Q is about the order of processing within PE1; I think it is:
First ATTEMPT to advertise all routes marking them with RT-EXP = 2; then put them through the local router's filter (export-map), that changes the RT from 2 to 5; then place them into MPBGP with RT = 5, only.
I don't think the router should then go back and check again the route against its RT-EXP statement that assigns "2" only... right? Otherwise it would be impossible to use an export-map that sets ExtCommunity without the "additive" keyword...
3- I have found this setup on some Cisco documentation (Ivan Pepelnjak, Jim Guichard MPLS and VPN Architectures, CCIP Edition 2000):
PE1
ip vrf lab
rd 100:1
export map VPN-A
The VPN-A map is defined, but no route-target export (or import) statements are configured in the vrf, at all; is it simply a typo/mistake or does it mean that the export-map is not only a filter, but it can actually "push" advertisements out, for assigned export-RT ?
4- this is the main Q of all for me; if the following is used as an import-map for a customer vrf:
route-map customer-imports permit 10
match ip address prefix-list abc
match extcommunity VoiceNets
route-map customer-imports deny 20
match extcommunity VoiceNets
route-map customer-imports permit 30
match ip address prefix-list Management-Addresses
match extcommunity Mon
route-map customer-imports deny 40
match extcommunity Mon
route-map customer-imports permit 50
I would like to know the exact meaning of the DENY clauses; for ex. statement 20, does it mean: do not import any prefixes from vrf VoiceNets (except those already imported thanks to statement 10), regardless what happens in the following clauses? Or does it mean: do not import them SO FAR, unless a broader permit statement (such as #50, "permit any") allows it? I suspect the former is correct, but I'd like confirmation.
5- And for last I would really appreciate it if someone could indicate me a very good book to study details of BGP/MPLS/VPNs, as I have about 20 of them, and none of them goes deep enough into details. I would need the precision and clarity of authors such as Scott Morris, and the (few) ones like him....
Thanks in advance to whoever can help! (Forgive the capital letters here and there, it's only for clarity).
Luca
