05-03-2010 01:22 PM - last edited on 03-25-2019 04:10 PM by ciscomoderator
I've configured a Catalyst 3750 switch with equal-cost paths, learned via OSPF, to a remote destination. I know that by default, OSPF will load-balance over the two paths, and I've confirmed this with the following output:
RR-A#sh ip route 192.168.250.1
Routing entry for 192.168.250.1/32
Known via "ospf 100", distance 110, metric 102, type intra area
Last update from 172.16.10.6 on Tunnel2, 00:21:44 ago
Routing Descriptor Blocks:
* 172.16.10.6, from 192.168.250.1, 00:21:44 ago, via Tunnel2
Route metric is 102, traffic share count is 1
172.16.10.2, from 192.168.250.1, 00:21:44 ago, via Tunnel1
Route metric is 102, traffic share count is 1
My question is, how do I know if the switch is load-balancing using per-packet or per-destination? From what I've read, it sounds like per-destination is the default, but I'm wondering if there's some command that will confirm that for me.
Thanks.
05-03-2010 01:30 PM
It's doing per-destination load-balancing because the 3750 does not support per-packet load-balancing - see the unsupported interface commands in this link ie. the "ip load-sharing per-packet" command is not supported -
3750 interface unsupported commands
Jon
05-03-2010 01:35 PM
Very well, that's all I wanted to know. Thanks for the quick reply.
05-03-2010 02:37 PM
Hello Pweinhold,
be aware that using GRE tunnels on a C3750 is acceptable in a lab, but not in a production environment: packets routed over GRE tunnels are processed in software.
The end result could even be similar to per packet destination for the fact of using GRE tunnels (process switching), it would be flow based destination if using other types of L3 interfaces like SVI or routed ports.
Hope to help
Giuseppe
05-03-2010 03:28 PM
Yes, this is just a lab environment, just to test out a proof-of-concept, but thanks for the heads-up.
05-03-2010 11:08 PM
Hi
The below command shows that the " Per packet load-sharing is disabled " so per session is working by default and if you enable per packet load sharing in the interface level then you can able to see the flow on the sh ip cef command ; try the same !!!!
Router#sh cef interface
XXXXXXXXXXXXXXXXXXXXXXXX
ICMP redirects are never sent
Per packet load-sharing is disabled
IP unicast RPF check is disabled
Inbound access list is not set
Outbound access list is not set
Hardware idb is GigabitEthernet0/0
Fast switching type 1, interface type 27
IP CEF switching enabled
IP CEF Feature Fast switching turbo vector
Input fast flags 0x400040, Input fast flags2 0x0, Output fast flags 0x10100, Output fast flags2 0x0
ifindex 1(1)
Slot 0 Slot unit 0 Unit 0 VC -1
Transmit limit accumulator 0x0 (0x0)
IP MTU 1500
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