FRRNode Protection

With FRR for Node Protection, you are not trying to protect only one link, but rather a whole router. Node protection works by creating a next-next-hop (NNHOP) backup tunnel. An NNHOP backup tunnel is not a tunnel to the next-hop router of the PLR, but to the router that is one hop behind the protected router. Therefore, in the case of node protection, the NNHOP router is the MP router. When you configure the command tunnel mpls traffic-eng fast-reroute node-protect on the head end of the TE tunnel, it sets the flag to 0x10 in the Session attribute of the PATH messages, indicating that it wants node protection.

Look at Figure 8-19, which has one NNHOP backup tunnel protecting the router berlin.

Figure 8-19 Node Protection

Resv

Label Subobject Label 31

paris brussels

paris brussels

MP

'■f -

pa

10.200.202.2 ^

rome

sydney

One TE tunnel goes from router paris to router sydney. An NNHOP backup tunnel 2000 goes from router brussels (the PLR) to router rome (the NNHOP and the MP). This backup tunnel avoids router berlin altogether by specifying the router berlin in the explicit path as excluded. This is done by specifying the MPLS TE router ID of router berlin as an excluded IP address in the explicit path.

Two issues make node protection a bit more complicated. The first issue is that the packets no longer arrive at the NHOP LSR, but at the NNHOP LSR. This means that the PLR somehow must learn the correct label to use for the NNHOP backup tunnel so that the packets arrive with the same top label at the NNHOP router as when the NNHOP backup tunnel is not used. To solve this problem, the label is advertised in a label subobject in an RRO object in a RESV message from the NNHOP router to the PLR router. When packets come in on the PLR on the rerouted LSP, the

Label 33

Label 30

Label 31

P Packet

IP Packet

P Packet

IP Packet

TE Tunnel 1

PLR must swap the incoming label with this label first and then push the label of the NNHOP backup tunnel. The second issue is that the backup tunnel is avoiding a router altogether that was on the rerouted LSP. The ERO in the PATH messages still holds the IP addresses of the protected router, even though that router is bypassed. The PLR must send the PATH messages onto the NNHOP tunnel for everything to keep working correctly. Figure 8-20 shows the packet forwarding when the PLR uses the NNHOP backup tunnel to forward traffic of TE tunnel 1.

Figure 8-

paris

Label 33

IP Packet

TE Tunnel 1

Example 8-19 shows the configuration of the NNHOP tunnel on router brussels and the TE tunnel from router paris to router sydney.

Example 8-19 Backup Tunnel Configuration for Node Protection brussels#

interface Tunnel2000 ip unnumbered Loopback0 tunnel destination 10.200.254.6 tunnel mode mpls traffic-eng tunnel mpls traffic-eng path-option 1 explicit name exclude-berlin

interface POS10/3

20 Node Protection Active

NNHOP Backup Tunnel

NNHOP Backup Tunnel

brussels

berlin rome sydney

brussels

berlin rome sydney

Node Failure

Example 8-19 Backup Tunnel Configuration for Node Protection (Continued)

ip address 10.200.211.1 255.255.255.0 mpls traffic-eng tunnels mpls traffic-eng backup-path Tunnel2000 ip rsvp bandwidth 155000

ip explicit-path name exclude-berlin enable exclude-address 10.200.254.5

paris#

interface Tunnel1 ip unnumbered Loopback0 tunnel destination 10.200.254.7 tunnel mode mpls traffic-eng tunnel mpls traffic-eng autoroute announce tunnel mpls traffic-eng priority 7 7 tunnel mpls traffic-eng bandwidth 1000 tunnel mpls traffic-eng path-option 10 explicit name one tunnel mpls traffic-eng fast-reroute node-protect

ip explicit-path name one enable next-address 10.200.210.2 next-address 10.200.211.2 next-address 10.200.215.2 next-address 10.200.202.2

Example 8-20 includes a traceroute across TE tunnel 1 to prove that the packets receive two labels instead of one when the backup tunnel is active. Also, whether the backup tunnel is in use or not, the packets on the TE tunnel 1 arrive on router rome with label 31 as the top label, even though the incoming interface is different when the TE LSP is rerouted versus when it is not.

Example 8-20 Verifying the NNHOP Tunnel paris#show mpls traffic-eng tunnels tunnel 1 protection paris_t1

LSP Head, Tunnel1, Admin: up, Oper: up

Src 10.200.254.2, Dest 10.200.254.7, Instance 1223

Fast Reroute Protection: Requested

Outbound: Unprotected: no backup tunnel assigned LSP signalling info:

Original: out i/f: PO4/0, label: 33, nhop: 10.200.210.2

nnhop: 10.200.215.1; nnhop rtr id: 10.200.254.6 Path Protection: None brussels#show mpls traffic-eng fast-reroute database detail LFIB FRR Database Summary: Total Clusters: 1

Total Groups: 1

Total Items: 1

LSP identifier 10.200.254.2 1 [1223], ready

Input label 33, Output label PO10/3:17, FRR label Tu2000:31

brussels#show ip rsvp fast-reroute

Primary Protect BW Backup

Tunnel I/F BPS:Type Tunnel:Label State Level Type rome_t1 PO10/2 0:G None None None paris_t1 PO10/3 1M:G Tu2000:31 Ready any-unl N-Nhop

!Traceroute when the NNHOP backup tunnel is not used paris#traceroute 10.200.254.7

Type escape sequence to abort. Tracing the route to 10.200.254.7

1 10.200.210.2 [MPLS: Label 33 Exp 0] 24 msec 24 msec 24 msec

2 10.200.211.2 [MPLS: Label 30 Exp 0] 24 msec 24 msec 24 msec

3 10.200.215.2 [MPLS: Label 31 Exp 0] 0 msec 0 msec 0 msec

!Traceroute when the NNHOP backup tunnel is not used paris#traceroute 10.200.254.7

Type escape sequence to abort. Tracing the route to 10.200.254.7

1 10.200.210.2 [MPLS: Label 33 Exp 0] 24 msec 24 msec 24 msec

2 10.200.212.2 [MPLS: Labels 17/31 Exp 0] 24 msec 24 msec 24 msec

3 10.200.214.2 [MPLS: Label 31 Exp 0] 0 msec 0 msec 4 msec

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