c7500: L3VPN recursive rewrite on RSP4/R5000's FEIP

[lunarman_98]

does any of you know what 'recursive rewrite' mean?

simple setup L3vpn, PE1-P-PE2.

in PE1 i use c7500 which has GE and FE interfaces. PE1 can't reach PE2's vrf_1 if FE is used. GE is ok. i found the following, which points to the difference between GE and FE being the uplink to P router. GE will impose tag properly and thus, work accordingly but FE shows it used 'recursive rewrite' instead.

i wonder if FEIP supports double tags.

thanks for any direction.

pe1_cisco#sho inter fastEthernet 1/1

FastEthernet1/1 is up, line protocol is up

Hardware is cyBus FastEthernet Interface, address is 0060.2fde.6d21 (bia 0060.2fde.6d21)

Internet address is 130.9.0.2/30

MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 100Mb/s, 100BaseTX/FX

pe1_cisco#sho mpls forwarding-table 50.0.0.1 detail

Local Outgoing Prefix Bytes tag Outgoing Next Hop

tag tag or VC or Tunnel Id switched interface

16 Untagged 50.0.0.1/32 0 Fa1/1 130.9.0.1

MAC/Encaps=0/0, MRU=1504, Tag Stack{}

No output feature configured

Per-packet load-sharing

pe1_cisco#sho ip cef vrf vrf_1 150.13.13.1 detail

150.13.13.1/32, version 203, epoch 0, cached adjacency 130.9.0.1

0 packets, 0 bytes

tag information set

local tag: VPN-route-head

fast tag rewrite with

Recursive rewrite via 50.0.0.1/32, tags imposed {816129}

via 50.0.0.1, 0 dependencies, recursive

next hop 130.9.0.1, FastEthernet1/1 via 50.0.0.1/32

valid cached adjacency

tag rewrite with

Recursive rewrite via 50.0.0.1/32, tags imposed {816129}

pe1_cisco#sho mpls forwarding-table vrf vrf_1 150.13.13.1 detail

Local Outgoing Prefix Bytes tag Outgoing Next Hop

tag tag or VC or Tunnel Id switched interface

None Recursive 150.13.13.1/32 0

Recursive rewrite via 50.0.0.1/32, Tag Stack{816129}

C7401000

No output feature configured

Per-packet load-sharing

[mheusinger]

Hi,

the recursive rewrite usually refers to a situation, where more than one IGP path to the BGP next hop is available. Basically CEF informs you, that the VPN label will be inserted behind the proper BGP next hop label.

In your case you can see those with "show ip cef 50.0.0.1 detail".

I would assume you have at least two different labels from two different neighbor routers to reach 50.0.0.1.

Hope this helps! Please rate all posts.

Regards, Martin

[lunarman_98]

thanks Martin, but for some reason, the tag works now after a reload. i was in the right direction, but wasn't sure if it has something to do with hardware limitation.

the answer is NOT. here's what the fec looks like now:

pe1_cisco#sho mpl for 50.0.0.1 detail

Local Outgoing Prefix Bytes tag Outgoing Next Hop

tag tag or VC or Tunnel Id switched interface

21 101280 50.0.0.1/32 0 Fa1/1 130.9.0.1

MAC/Encaps=14/18, MRU=1500, Tag Stack{101280}

009069ACC45D00602FDE6D218847 18BA0000

No output feature configured

Per-packet load-sharing