updates for VRFs absent from local device are dropped, saving RAM; does not apply to RR
when prefix is redistributed into VPNv4, PE create a new prefix from it, VPNv4 NLRI ⇒ no need for next-hop-self
RT:
route-target
format of RD, may be different from RD
extended community (8 bytes)
mark on the prefix, used for VRF import/export
LFIB is shared between VRFs
MPLS label is allocated when prefix is added to BGP VRF RIB, label is exchanged via BGP
(config)# ip vrf <NAME>
(config-vrf)# rd <ASN>:<num>
(config-vrf)# route-target import|export|both <RT>
; different next-hops for different VRF (e.g. tail for TE tunnels)
(config-vrf)# bgp next-hop <intf>
; per-vrf enables using 1 label for all prefixes for VRF, per-prefix by default
(config)# mpls label all-vrfs|vrf <NAME> protocol bgp-vpnv4 per-prefix|per-vrf
(config-router)# address-family ipv4 vrf <NAME>
(config-router-af)# redistribute eigrp 1
; import period for VPNv4 VRF prefixes, 60s by default
(config-router-af)# bgp scan-time impotr <sec>
(config-router)# address-family vpnv4
; IP-based, even if neighbour in peer-group
(config-router-af)# neighbor <IP> activate
(config-router-af)# neighbor <IP> send-community
; disables dropping NLRI for unused RT (e.g. Inter-AS VPN Option B)
(config-router)# no bgp default route-target filter
# show ip bgp vpnv4 all [labels]
Route distinguisher (RD)
2 bytes
2 bytes
4 bytes
Type 0
ASN
Value
Type 1
IP
Value
Type 2
ASN
Value
6VPE
BGP next-hop = IPv4-mapped IPv6
MPLS over mGRE
does not use NHRP (uses BGP for discovery) or LDP
spoke-to-spoke
VPNv4/v6, spokes – PE
MDT mcast (GRE)
(config)# l3vpn encapsulation ip <name>
transport ipv4 source <intf>
protocol gre key <n>
(config-route-map)# set ip next-hop encapsulate l3vpn <NAME>
(config-router-af)# neighbor <IP> route-map <MAP> in
Route-leaking
between VRF – RT, origin is preserved on import
between VRF and global:
static routes
EVN route-replicate
PBR
import/export map (ipv4 unicast map)
internet access:
separate VRF
route-leak
dot1q/GRE
on importing from local VRF, route is eBGP
; by default tunnel endpoint are searched for in global VRF
(config-if)# tunnel vrf <NAME>
; on by default, permits setting interfaces from other VRFs as next-hop
(config)# ip route static inter-vrf
; next-hop in global VRF
(config)# ip route vrf <NAME> <prefix> <next-hop> global
; next-hop can be in another VRF
(config)# ip route <prefix> <next-hop>
; route-leak between VRF and global, permitted routes are not reexported into VPNv4, prefixes must be in BGP RIB (global/VRF)
(config-vrf)# import ipv4 unicast map <MAP>
(config-vrf)# export ipv4 unicast map <MAP>
; filtering prefixes between VRF
(config-vrf)# import map <MAP>
(config-vrf)# export map <MAP>
(config-vrf)# maximum routes <n> <threshold>
; sets RT on exporting
(config-map)# set extcommunity rt <RT>
Route reflector
receives all prefixes from the clients (including with unused RT)
load-sharing via RR group, distribution based on RT (e.g. odd/even)
(config)# ip extcommunity-list standard <NAME> permit|deny rt <RT>
; not needed on RR
(config-router)# no bgp default route-target filter
(config-router)# address-family vpnv4
; uses extcommunity-list for filtering
(config-router-af)# bgp rr-group <NAME>
; IP-only activation
(config-router-af)# neighbor <IP> activate
; parameters can be applied to group
(config-router-af)# neighbor <PEER route-reflector-client
Best-path external
allows announcing best eBGP path instead of bestpath
installs bext-external as backup in CEF and RIB (enables PIC) if next-hop is different from primary next-hop
per-prefix label allocation is required on backup PE (enables label forwarding), otherwise – routing loop because of IP forwarding
active-standby connection
multipath has more priority over backup eBGP
no support for L2VPN, NSF, RR
; global VRF, if in VPN AF – for all VRF, if in VRF AF – only for this specific VRF
(config-router)# bgp advertise-best-external
; does not enable best-external! part of Diverse path
(config-router)# neighbor <IP> advertise best-external
Local convergence
no support for IS-IS routes
IPv6 routes – only static and eBGP
pre-PIC technology
does not remove labels from LFIB for 5 mins after prefix is lost
selects locally a backup route, does not push it into FIB/RIB, uses for rerouting traffic