This may be old news to you guys but I had never seen the “traffic-share min across-interfaces” command before. I was messing about with EIGRP unequal cost load-sharing the other day and came across it.
r1(config-router)#traffic-share ?
balanced Share inversely proportional to metric
min All traffic shared among min metric paths <-what’s this?
r1(config-router)#traffic-share min ?
across-interfaces Use different interfaces for equal-cost paths
r1(config-router)#traffic-share min across-interfaces
Weird. It turns off unequal-cost load balancing by not allowing traffic over the Feasable Successor route(s) regardless of the variance command:
r1(config-router)#var 4
*Mar 2 00:05:02.000: %FIB-4-UNEQUAL: Range of unequal path weightings too large for prefix 150.1.6.0/24. Some available paths may not be used.
r1(config-router)#do sh ip route 164.1.26.0 255.255.255.0
Routing entry for 164.1.26.0/24
Known via “eigrp 100”, distance 90, metric 3026432, type internal
Redistributing via eigrp 100
Last update from 164.1.12.2 on Serial0/0, 00:00:03 ago
Routing Descriptor Blocks:
* 164.1.13.3, from 164.1.13.3, 00:00:03 ago, via Serial0/1
Route metric is 3026432, traffic share count is 1
Total delay is 40100 microseconds, minimum bandwidth is 1280 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 2
164.1.12.2, from 164.1.12.2, 00:00:03 ago, via Serial0/0
Route metric is 10514432, traffic share count is 0
Total delay is 20100 microseconds, minimum bandwidth is 256 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 1
r1(config-router)#var 40
r1(config-router)#do sh ip route 164.1.26.0 255.255.255.0
Routing entry for 164.1.26.0/24
Known via “eigrp 100”, distance 90, metric 3026432, type internal
Redistributing via eigrp 100
Last update from 164.1.12.2 on Serial0/0, 00:00:02 ago
Routing Descriptor Blocks:
* 164.1.13.3, from 164.1.13.3, 00:00:02 ago, via Serial0/1
Route metric is 3026432, traffic share count is 1
Total delay is 40100 microseconds, minimum bandwidth is 1280 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 2
164.1.12.2, from 164.1.12.2, 00:00:02 ago, via Serial0/0
Route metric is 10514432, traffic share count is 0
Total delay is 20100 microseconds, minimum bandwidth is 256 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 1
Similarly, when you use the traffic-share command with the keyword min, the traffic is sent only across the minimum-cost path, even when there are multiple paths in the routing table.
router eigrp 1
network x.x.x.x
variance 3
traffic-share min across-interfaces
In this situation, EIGRP sends packets only through E-C-A, which is the best path to the destination network. This is identical to the forwarding behavior without use of the variance command. However, if you use the traffic-share min command and the variance command, even though traffic is sent over the minimum-cost path only, all feasible routes get installed into the routing table, which decreases convergence times.
It turns out that this command is available for all routing protocols.
r1(config)#router os 100
r1(config-router)#traffic-share min ?
across-interfaces Use different interfaces for equal-cost paths
r1(config)#router rip
r1(config-router)#traffic-share min ?
across-interfaces Use different interfaces for equal-cost paths
Nice explanation, hope your studies are going well 🙂
Comment by galvezc — September 15, 2008 @ 9:40 am |