Re: Problems on load sharing for static routes

jmagnaye · ‎11-27-2003

I have a network with /26, and is using 2x3660 routers. I only have bunch of T1s. 5xT1s connected on 3660-1 going to ISP1, and 5xT1s connected to 3660-2 going to ISP1 (as well). I don't have extra port on either 3660, so I cannot merge all T1s on single 3660. I enabled IP CEF ALGORITHM ORIGINAL on global, IP CEF LOAD-SHARING PER PACKET and IP ROUTE-CACHE FLOW on my Serial interfaces. The following are my issues:

A. My static route:

ip route 0.0.0.0 0.0.0.0 Serial1/0

ip route 0.0.0.0 0.0.0.0 Serial2/0

ip route 0.0.0.0 0.0.0.0 Serial3/1

ip route 0.0.0.0 0.0.0.0 Serial4/0

ip route 0.0.0.0 0.0.0.0 Serial4/1

Problem: when I do sho ip route, im only seeing:

S* 0.0.0.0/0 is directly connected, Serial1/0

is directly connected, Serial2/0

is directly connected, Serial3/1

is directly connected, Serial4/0

(Same what appears on my 2nd router. The last static route do not appear on the sho ip route)

B. from my mrtg, i see that my outbound traffic is well balanced. but my inbound is not. i only have one isp and they also turned on the cef. but they are saying that the reason for the unbalanced traffic is because they're doing cef on single subnet (my /26) that has two different routers. can someone clarify that? i am not convinced.

thanks in advance for anyone who could post and help.

lahenche · ‎11-27-2003

Hi,

by default you can only balance traffic up to 4 routes with the same metric. That's why you can only see 4 routes with 'sh ip route' command. However it's possible to increase this limit up to 6 routes with the command 'max-paths'.

Regarding your incoming traffic I'm affraid I can't help you too much.

Bye,

ruwhite · ‎11-27-2003

The max should now be 8, and I wouldn't use per packet load sharing. It will cost you more in flow performance than you are gaining in link performance, since it will most likely cause your packet to arrive out of order.

:-)

Russ.W

jmagnaye · ‎12-01-2003

what do you suggest then? my traffic is mostly voip.

ccobb258 · ‎12-02-2003

"what do you suggest then? my traffic is mostly voip."

If your doing load balancing for VOIP and on a per packet basis ... your doing it all wrong. VOIP QOS is an entirely different animal altogether. ppp multilink is the best option for that. If your doing VOIP over the internet, your going to hate VOIP.

24madaeve1 · ‎12-22-2014

can anyone guide me how to use per-flow load sharing between two data centers connected through two MPLS links from different ISPs ? Or if you could come up with a load sharing mechanism across both the WAN links. I have configured my WAN links statically. I cant configure them using any other routing protocol.

24madaeve1 · ‎12-22-2014

can you guide me how to use per-flow load sharing between two data centers connected through two MPLS links from different ISPs ? Or if you could come up with a load sharing mechanism across both the WAN links. I have configured my WAN links statically. I cant configure them using any other routing protocol.

jmagnaye · ‎12-01-2003

isn't this for rip and some other dynamic protocol? does it apply for static as well? if it does, where is it available -- global?

ruwhite · ‎12-01-2003

Actually, it should be for any and all routes, but I don't see any way to configure it for static routes, which is interesting. I'll have to file a defect on that, and ask the coders that manage the static route code to add a command that allows it to be configured.

:-)

Russ.W

ruwhite · ‎12-01-2003

So, going back to the original question, I see a couple of things. First, it doesn't make any sense to me that you have 6 statics configured, and only three show up. When I try this in the lab, I get all 6 of them. I can't get 8, but I can get 6, on a fairly late version of code. Three is an odd number, in any case, and makes me suspicious that there is more here than meets the eye.

Could you post the output of a show ip interfaces brief?

On the second question, they ISP is probably telling what they are seeing, which is how they are routing to you from their end. They are probably doing per source/destination load sharing in CEF, rather than per packet. I wouldn't do per packet, anyway, as I've said elsewhere.

But it's interesting because they should be seeing at least some split--do you know what the actual pecentages of utilization are between the two routers?

Russ.W

ruwhite · ‎12-04-2003

I've filed CSCed16342 on being able to install 8 static routes, and also to be able to set the mximum number of static routes that will be installed in the routing table.

Russ.W