Jan 2 2009
ISIS wide metrics
Be default ISIS caps ISIS metrics greater than 63.
To address this limitation a new IS-IS TLV was defined to overcome the limited 6-bit metric of 63. This TLV known as TLV Type 135 increased the per-link metric range from <0-63> to <1-16777214> ie the new TLV has 24-bits for the ISIS metric.
This new range can be seen under the interface config mode as shown below.
R2(config)#interface loopback 0
R2(config-if)#isis metric ?
<1-16777214> Default metric
Consider the topology below.
We will attempt to increase the metric of the R2 loopback to greater than 63 with and without wide-metrics enabled.
The video below shows how to configure and verify the use of wide metrics in ISIS. Click here to download the video and watch it on your iPod.
The commands used in the video are as below:-
R1
interface FastEthernet1/0
ip router isis
!
router isis
net 49.0001.0000.0000.0001.00
is-type level-2-only
metric-style wide
passive-interface Loopback0de>
R2
interface Loopback0
isis metric 10000
!
interface FastEthernet1/0
ip router isis
!
router isis
net 49.0001.0000.0000.0002.00
is-type level-2-only
metric-style wide
passive-interface Loopback0
R3
interface FastEthernet1/0
ip router isis
!
interface FastEthernet1/1
ip router isis
!
router isis
net 49.0001.0000.0000.0003.00
is-type level-2-only
metric-style wide
passive-interface Loopback0
!
To verify the wide metric on R1 use the command below.
R1#show isis database R2.00-00 detail
IS-IS Level-2 LSP R2.00-00
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
R2.00-00 0x0000000E 0x1A31 428 0/0/0
Area Address: 49.0001
NLPID: 0xCC
Hostname: R2
IP Address: 2.2.2.2
Metric: 10 IS-Extended R3.02
Metric: 10000 IP 2.2.2.2/32
Metric: 10 IP 10.0.0.4/30
