Configuring the Unequal Cost Multi Path (UCMP) Local
Perform the following task to configure the ucmp local:
router isis
ucmp local [prefix-list <prefix-list-name>]
router isis
address-family ipv6
ucmp local [prefix-list <prefix-list-name>]
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The Cisco IOS XE ISIS Local UCMP feature allows you to load balance traffic from A1 to A2, across all the links from A1-C1 and A1-C2 in a network. When you configure equal metrics on all the links, it will create Equal Cost Multipath (ECMP) paths. However, the higher bandwidth links will carry the same traffic as the lower bandwidth links and the higher bandwidth links are underutilized. To avoid this problem, you can configure all the links to distribute the traffic proportionately across the links based on bandwidth, even if the configured metrics on all links are the same.
The following figure explains the topology:
Perform the following task to configure the ucmp local:
router isis
ucmp local [prefix-list <prefix-list-name>]
router isis
address-family ipv6
ucmp local [prefix-list <prefix-list-name>]
To verify the feature, use the following show commands:
show interface <name> counters
show ip route
show ipv6 route
show ip cef
show mpls forwarding-table labels detail
show mpls infrastructure lfd lte
The following is a sample output from the show ip route of the Unequal Cost Multi Path (UCMP) Local:
Device#show ip route 10.138.1.3
Routing entry for 10.138.1.0/24
Known via "isis", distance 115, metric 50, type level-1
Redistributing via isis Ring#1
Advertised by isis Ring#1 (self originated)
Last update from 10.148.1.1on FortyGigabitEthernet0/5/1, 00:24:51
ago
Routing Descriptor Blocks:
* 10.198.1.1, from 10.1.1.1, 00:24:51 ago, via GigabitEthernet0/0/0
Route metric is 50, traffic share count is 6
10.148.1.1, from 10.1.1.1, 00:24:51 ago, via
FortyGigabitEthernet0/5/1
Route metric is 50, traffic share count is 25
![]() Note |
You should verify if the traffic share count is computed according to the interface bandwidth. |
The following is a sample output from show interface counter of the Unequal Cost Multi Path (UCMP) Local:
Device#show interface fo0/5/1 counters
Port InOctets InUcastPkts InMcastPkts InBcastPkts
Fo0/5/1 22883 0 17 0
Port OutOctets OutUcastPkts OutMcastPkts OutBcastPkts
Fo0/5/1 16242883 57513 17 0
PE12#show interface gi0/0/0 counters
Port InOctets InUcastPkts InMcastPkts InBcastPkts
Gi0/0/0 26388 26 19 0
Port OutOctets OutUcastPkts OutMcastPkts OutBcastPkts
Gi0/0/0 81944464 264216 195 0
![]() Note |
You can verify if the outgoing traffic is split according to the computed traffic share count. |
To troubleshoot the issues related to local UCMP, use the following debug commands:
debug isis mfi
debug ip routing detail
debug ipv6 routing
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to https://cfnng.cisco.com/. An account on Cisco.com is not required.
Feature Name |
Releases |
Feature Information |
---|---|---|
Segment Routing—IS-IS UCMP |
Cisco IOS XE 17.5.1 |
The Segment Routing—IS-IS UCMP feature allows you to load balance outgoing traffic across all IGP ECMP paths proportionally to the interface bandwidth. |