2013年7月24日星期三

Load Balancing across GRE Tunnels, EIGRP

Question:

First post here and cisco ios commands I did do a search, but didnt come up with much.

I have two GRE tunnels across 2 seperate WAN links. One link is 45 Mbps and the other link is 6Mpbs. I was thinking the Variance command would be the choice here(well only choice)  since we are running EIGRP.

Below are the (Edited)configs on the spokes

First tunnel

INTERFACE TUNNEL 10500
DESCRIPTION 45Mbps
DAMPENING
BANDWIDTH 45000
IP ADDRESS X.X.X.X
TUNNEL SOURCE X.X.X.30
TUNNEL MODE IPSECIPV4
TUNNEL DESTINATION X.X.X.29
SERVICE POLICY OUTPUT SHAPING-45000

Second Tunnel

INTERFACE TUNNEL 10501
DESCRIPTION 6Mbps
DAMPENING
BANDWIDTH 6312
IP ADDRESS X.X.X.X.
TUNNEL SOURCE SERIAL 0/0/0
TUNNEL DESTINATION X.X.X.46
SERVICE POLICY OUTPUT SHAPING-6312

This is my first project for my new job, so I obviously want to get it right. If I am missing some critical information or you need clarification on something, please do not hesitate to request it.

Thanks in advance


Answer:

If you do a sh ip route eigrp  at present their should be only on path for all routes in the rib table.

Now when you apply a variance value this will install another path into the rib, meaning you will then have two paths showing in the routing table.

The variance calculation can be done by the metric extracted from the Eigrp topology table:
P 10.170.9.24/30, 1 successors, FD is 1345280
       via 10.170.2.50 (1345280/65280), Tunnel10500, serno 72548
       via 10.170.2.56 (1688576/65280), Tunnel10501, serno 72568

1345280/1688576 =1.25 round out the highest value =  variance 2

@Richard/Joseph
I think what I am trying to get at, is with or without the variance, CEF will default to forward via per destination anyway. I agree deterministically if the variance is applied and a new path is now availble, another scr/dst could use this new path, BUT wouldnt this other scr/dst always use that same path, and not load share between the two without per-packet...correct???


(by the way in my testing Cisco Switches Price i used a variance of 9)

没有评论:

发表评论