Nov 30 2008

Configuring Traffic Engineering

Consider the toplogy below.

We will enable traffic engineering on the serial link between PE1 and P1 and between P1 and PE2.

The first step is to enable traffic engineering globally on all three routers using the command below.

mpls traffic-eng tunnels

Once you have enabled traffic engineering globally, you then need to enable traffic engineering on all the infrastructure links using the command below.

interface Serial1/0.1 point-to-point mpls traffic-eng tunnels

Once you have enabled traffic engineering on the interface you need to decide how much bandwidth per interface you will allow the traffic engineering tunnels to reserve. This can be done with the commands below.

interface Serial1/0.1 point-to-point ip rsvp bandwidth 512

The rsvp value configured here is advertised by IS-IS sub-TLV 10 which is encoded within TLV22. Sub-TLV 9 which is also encoded within TLV22 advertises the Maximum bandwidth of the interface which can be seen as below.

Serial1/0.1 is up, line protocol is up Hardware is M8T-X.21 Internet address is 10.0.0.2/30 MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation FRAME-RELAY Keepalive set (10 sec) Last clearing of "show interface" counters never

We can now view the Traffic Engineering Topology which is constructed using the TE extensions.

if we examine P1s topology we can see two links. It is also worth noting that each link has a TE metric as well as an IGP metric. Also you will notice there are 8 bandwidth entries for each link. We will examine these later, for now its enough to now that they are linked to the priorities of the reservations.

Also worth noting is that currently there are no bandwidth reservations as we havent set up any TE tunnels.

PE1#show mpls traffic-eng topology 2.2.2.2

IGP Id: 0000.0000.0002.00, MPLS TE Id:2.2.2.2 Router Node (isis level-2) id 2 link[0]: Point-to-Point, Nbr IGP Id: 0000.0000.0001.00, nbr_node_id:1, gen:2 frag_id 0, Intf Address:10.0.0.2, Nbr Intf Address:10.0.0.1 TE metric:10, IGP metric:10, attribute flags:0x0 physical_bw: 1544 (kbps), max_reservable_bw_global: 512 (kbps) max_reservable_bw_sub: 0 (kbps)

Global Pool Sub Pool Total Allocated Reservable Reservable BW (kbps) BW (kbps) BW (kbps) --------------- ----------- ---------- bw[0]: 0 512 0 bw[1]: 0 512 0 bw[2]: 0 512 0 bw[3]: 0 512 0 bw[4]: 0 512 0 bw[5]: 0 512 0 bw[6]: 0 512 0 bw[7]: 0 512 0

link[1]: Point-to-Point, Nbr IGP Id: 0000.0000.0003.00, nbr_node_id:3, gen:2 frag_id 0, Intf Address:10.0.0.5, Nbr Intf Address:10.0.0.6 TE metric:10, IGP metric:10, attribute flags:0x0 physical_bw: 100000 (kbps), max_reservable_bw_global: 1000 (kbps) max_reservable_bw_sub: 0 (kbps)

Global Pool Sub Pool Total Allocated Reservable Reservable BW (kbps) BW (kbps) BW (kbps) --------------- ----------- ---------- bw[0]: 0 1000 0 bw[1]: 0 1000 0 bw[2]: 0 1000 0 bw[3]: 0 1000 0 bw[4]: 0 1000 0 bw[5]: 0 1000 0 bw[6]: 0 1000 0 bw[7]: 0 1000 0

We will now setup a TE tunnel with a bandwidth reservation of 256Kb with the head end of the tunnel on PE1.

interface Tunnel100 ip unnumbered Loopback0 tunnel destination 3.3.3.3 tunnel mode mpls traffic-eng tunnel mpls traffic-eng priority 7 7 tunnel mpls traffic-eng bandwidth 256 tunnel mpls traffic-eng path-option 1 dynamic end

Once the tunnel has came up, let us reexamine the traffic engineering toplogy of node P1.

PE1#show mpls traffic-eng topology 2.2.2.2
IGP Id: 0000.0000.0002.00, MPLS TE Id:2.2.2.2 Router Node (isis level-2) id 2 link[0]: Point-to-Point, Nbr IGP Id: 0000.0000.0001.00, nbr_node_id:1, gen:4 frag_id 0, Intf Address:10.0.0.2, Nbr Intf Address:10.0.0.1 TE metric:10, IGP metric:10, attribute flags:0x0 physical_bw: 1544 (kbps), max_reservable_bw_global: 512 (kbps) max_reservable_bw_sub: 0 (kbps)

link[1]: Point-to-Point, Nbr IGP Id: 0000.0000.0003.00, nbr_node_id:3, gen:4 frag_id 0, Intf Address:10.0.0.5, Nbr Intf Address:10.0.0.6 TE metric:10, IGP metric:10, attribute flags:0x0 physical_bw: 100000 (kbps), max_reservable_bw_global: 1000 (kbps) max_reservable_bw_sub: 0 (kbps)

As you can see, a reservation of 256Kb is confirmed on the outgoing and NOT incoming interface on P1.

Also, the reservable bandwidth on link[1] has descreased to 744Kb.

Now lets see what happens if we setup another tunnel between PE1 and PE2, however this time we will give the tunnel a priority value of 5 and we will reserve 256Kb for this new tunnel.

The new tunnel will be configured as follows.

interface Tunnel200 ip unnumbered Loopback0 tunnel destination 3.3.3.3 tunnel mode mpls traffic-eng tunnel mpls traffic-eng priority 5 5 tunnel mpls traffic-eng bandwidth 256 tunnel mpls traffic-eng path-option 1 dynamic

Now lets examine the TE topology for node P1.

PE1#show mpls traffic-eng topology 2.2.2.2

IGP Id: 0000.0000.0002.00, MPLS TE Id:2.2.2.2 Router Node (isis level-2) id 2 link[0]: Point-to-Point, Nbr IGP Id: 0000.0000.0001.00, nbr_node_id:1, gen:6 frag_id 0, Intf Address:10.0.0.2, Nbr Intf Address:10.0.0.1 TE metric:10, IGP metric:10, attribute flags:0x0 physical_bw: 1544 (kbps), max_reservable_bw_global: 512 (kbps) max_reservable_bw_sub: 0 (kbps)

link[1]: Point-to-Point, Nbr IGP Id: 0000.0000.0003.00, nbr_node_id:3, gen:6 frag_id 0, Intf Address:10.0.0.5, Nbr Intf Address:10.0.0.6 TE metric:10, IGP metric:10, attribute flags:0x0 physical_bw: 100000 (kbps), max_reservable_bw_global: 1000 (kbps) max_reservable_bw_sub: 0 (kbps)

As you can see for link[1] there are now 2 reservations, one at priority level 5 and the other at priority level 7.

The other interesting thing to note is the reservable bandwidth values for priority 5 and 7. Priority 7 tunnels now only have 488Kb of reservable bandwidth available whereas priority 5 tunnels have 744Kb of bandwidth available to them. This is due to the fact that priority 5 tunnels have more priority to the bandwidth than priority 7 tunnels. If another priority 5 tunnel requests 744Kb of bandwidth it will receive the bandwidth and the priority 7 tunnel will be “bumbed” ie will have to find another route through the network and if it cannot then it will show as down.

The last thing to do to make the TE tunnel active is to announce the tunnel with the IGP as follows.

interface Tunnel100 tunnel mpls traffic-eng autoroute announce

If we now check the routing table we can see that some routes are visible behind tunnel 100.

PE1#show ip route 1.0.0.0/32 is subnetted, 1 subnets C 1.1.1.1 is directly connected, Loopback0 2.0.0.0/32 is subnetted, 1 subnets i L2 2.2.2.2 [115/10] via 10.0.0.2, Serial1/1.1 3.0.0.0/32 is subnetted, 1 subnets i L2 3.3.3.3 [115/20] via 3.3.3.3, Tunnel100 20.0.0.0/30 is subnetted, 1 subnets i L2 20.0.0.0 [115/20] via 10.0.0.2, Serial1/1.1 10.0.0.0/30 is subnetted, 2 subnets C 10.0.0.0 is directly connected, Serial1/1.1 i L2 10.0.0.4 [115/20] via 10.0.0.2, Serial1/1.1

However its worth noting, not all subnets are being routed via tunnel 100. I’ll cover this in another post, its important to know when enabling TE which prefixes will use the tunnels.

By zismail • CCIE SP, Traffic Engineering • 1 • Tags: CCIE SP, IS-IS, TE, Traffic Engineering

One Comment

Pramod Kumar
Apr 17, 2010 @ 17:21:23

Hi Ismail,

Can you please update this topic with the ” Verbatim mode Tunnel configuration ” as well.

This mode helps the N/W engg to create a TE across domains which does not have link state protocols runnig.

Regards,
Pramod
Independant Network Consultant

Configuring Traffic Engineering

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