Dual TE Metrics

By default, MPLS TE uses the TE metrics of the links to route the TE tunnels; however, by default the TE link metrics are the same as the IGP link metrics. However, you can override this option when you set the TE metrics. You cannot have two TE metrics, though, to route TE tunnels. One solution, if you want to use two metrics, is to use the IGP metric and TE metric at the same time to route TE tunnels. Network administrators who want one metric for delay and one for bandwidth choose this option. You can use the metric reflecting the delay of the links to indicate what the best paths are for TE tunnels carrying the voice traffic, because the voice traffic needs a small overall delay. You can use the other metric reflecting the bandwidth to indicate the best path for the TE tunnels that are carrying the bulk data traffic. Because the availability of both metric types exists, it is simply a matter of choosing which metric to use for each TE tunnel: the IGP or the TE metric. You do this with the traffic-eng path-selection metric {igp I te} command on the tunnel interface on the head end router. Example 8-10 shows this command.

Example 8-10 Configuring the path-selection Metric

london(config)#interface tunnel 1

london(config-if)#tunnel mpls traffic-eng path

selection ?

metric Metric type for path calculation

london(config-if)#tunnel mpls traffic-eng path

selection metric ?

igp Use IGP Metric

te Use TE Metric

Figure 8-8 shows an example of using both metric types.

Figure 8-8 Using the MPLS traffic-eng administrative-weight Command brussels berlin brussels berlin

MPLS Traffic-eng Administrative-weight 18

IGP Cost io frankfurt rome

Dynamic TE Tunnel (IGP Cost = 2)

frankfurt rome

The IGP cost of the links is mentioned next to the links. If traffic is routed from router brussels to router rome, the total IGP cost of the path is 2. The IP traffic that is routed from router brussels to rome takes the path brussels-berlin-rome. A TE tunnel from router brussels to rome also follows the path brussels-berlin-rome, because the TE metrics are the same as the IGP metrics by default. If you want to put the TE tunnel on the path brussels-frankfurt-rome instead, you can increase the IGP cost of the link berlin-rome so that the total TE cost of the path brussels-berlin-rome is higher than the path brussels-frankfurt-rome. However, changing the IGP cost influences all traffic— including the IP traffic. If you change the TE metric of the link berlin-rome to 18, the total cost of the path brussels-berlin-rome becomes 19. The preferred path for the tunnel from router brussels to router rome is now brussels-frankfurt-rome, with a cost of 18. The IP traffic still prefers the path brussels-berlin-rome; however, if you configure the tunnel to prefer the IGP cost, the path becomes brussels-berlin-rome again. Example 8-11 shows you this tunnel when using the TE metric as the basis for path calculation. As you can see, the path weight (metric) is 18.

Example 8-11 TE Metric berlin#conf t

Enter configuration commands, one per line. End with CNTL/Z. berlin(config)#int pos 0/0

berlin(config-if)#mpls traffic-eng administrative-weight 18

brussels#show mpls traffic-eng tunnels tunnel 1

Name: brussels_t1 Status: Admin: up

Oper: up Path: valid

(Tunnell) Destination: 10.200.254.6

Signalling: connected path option 1, type dynamic (Basis for Setup, path weight 18)

Example 8-11 TE Metric (Continued)

path option 1, delayed clean in progress

Config Parameters: Bandwidth: 0

kbps (Global) Priority: 7 7 Affinity: 0x0/0xFFFF

Metric Type: TE (default)

AutoRoute: disabled LockDown: disabled Loadshare: 0

bw-based auto-bw: disabled Active Path Option Parameters:

State: dynamic path option 1 is active

BandwidthOverride: disabled LockDown: disabled Verbatim: disabled

InLabel : -OutLabel : POS10/1, 36 RSVP Signalling Info:

Src 10.200.254.3, Dst 10.200.254.6, Tun_Id 1, Tun_Instance 3 RSVP Path Info:

My Address: 10.200.254.3

Explicit Route: 10.200.212.2 10.200.214.2 10.200.254.6 Record Route: NONE

Tspec: ave rate=0 kbits, burst=1000 bytes, peak rate=0 kbits RSVP Resv Info:

Record Route: NONE

Fspec: ave rate=0 kbits, burst=1000 bytes, peak rate=0 kbits Shortest Unconstrained Path Info: Path Weight: 18 (TE)

Explicit Route: 10.200.212.2 10.200.214.2 10.200.254.6

Look at Example 8-12. When you configure the path-selection command to instruct the TE tunnel to use the IGP metric instead of the TE metric, the TE tunnel 1 path weight (metric) becomes 2.

Example 8-12 Path-Selection Metric IGP

brussels(config)#interface tunnel 1

brussels(config-if)#tunnel mpls traffic-eng path-selection metric igp brussels(config-if)#~Z

brussels#show mpls traffic-eng tunnels tunnel 1

Name: brussels_t1 Status: Admin: up

Oper: up Path: valid

(Tunnell) Destination: 10.200.254.6

Signalling: connected path option 1, type dynamic (Basis for Setup, path weight 2)

Config Parameters: Bandwidth: 0

kbps (Global) Priority: 7 7 Affinity: 0x0/0xFFFF

Example 8-12 Path-Selection Metric IGP (Continued)

Metric Type: IGP (interface)

AutoRoute: disabled LockDown: disabled Loadshare: 0

bw-based auto-bw: disabled Active Path Option Parameters:

State: dynamic path option 1 is active

BandwidthOverride: disabled LockDown: disabled Verbatim: disabled

InLabel : -OutLabel : POS10/3, 22 RSVP Signalling Info:

Src 10.200.254.3, Dst 10.200.254.6, Tun_Id 1, Tun_Instance 4 RSVP Path Info:

My Address: 10.200.254.3

Explicit Route: 10.200.211.2 10.200.215.2 10.200.254.6 Record Route: NONE

Tspec: ave rate=0 kbits, burst=1000 bytes, peak rate=0 kbits RSVP Resv Info:

Record Route: NONE

Fspec: ave rate=0 kbits, burst=1000 bytes, peak rate=0 kbits Shortest Unconstrained Path Info: Path Weight: 2 (IGP)

Explicit Route: 10.200.211.2 10.200.215.2 10.200.254.6 brussels#show mpls traffic-eng topology 10.200.254.5

IGP Id: 10.200.254.5, MPLS TE Id:10.200.254.5 Router Node (ospf 1 area 0) id 46 link[0]: Point-to-Point, Nbr IGP Id: 10.200.254.6, nbr_node_id:52, gen:602 frag_id 0, Intf Address:10.200.215.1, Nbr Intf Address:10.200.215.2 TE metric:18, IGP metric:1, attribute_flags:0x0 SRLGs: None physical_bw: 155000 (kbps), max_reservable_bw_global: 155000 (kbps) max_reservable_bw_sub: 10000 (kbps)

Global Pool Total Allocated Reservable

Sub Pool Reservable BW (kbps)

155000 155000 155000 155000 155000 155000 155000 155000

0000 0000 0000 0000 0000 0000 0000 0000

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