Load balance over 2 routers

[robward]

Hi

Has anyone got any suggestions of how I can load balance between two separate routers that are going to the same location. There currently set up for fault tolerance using EIGRP, but this creates a problem of two default gateways. I'd like to have one default gateway that routes data to the remote site via both links. Is this possible?

Thanks for the help

Rob

 

[bell1996]

If I understand your situation correctly, you have a LAN segment with 2 routers. The 2 routers have a connection to a main site. If this is your scenario, then the best you can do is use HSRP for router redundancy and possibly create 2 standby groups. Have half the PC's on the LAN point to HSRP address #1 and the other half to HSRP address #2.

If I've gotten your scenario wrong, pls elaborate.

 

[Narizz28]

For load balancing, use GLBP if you have the hardware to handle IOS 12.3

GLBP sets a virtual MAC on all configured members and uses one Virtual IP address that you define. The first router configured becomes the AVG (Active Vitual Gateway), and all other members of the team become AVF's (Active Virtual Forwarders). When a device ARP requests the address, the AVG will respond (in default round robin mode) with the virtual MAC of the next AVF in line.

It should be noted that GLBP is pretty configurable outside it's default behaviors, so you could set it up so the AVG will respond to ARP requests from certain hosts with one AVF, and another AVF for other hosts.

I hope this helps. I am in the process of configuring this myself, but am waiting for more hardware.

 

[bell1996]

Narizz28

What type of hardware are you using? Is it a Cisco product?

 

[Narizz28]

When finished, this will be on two Cisco 1721 routers, each connected to a different T1 and both terminate to the same provider. IOS 12.3 on both routers.

 

[LeighH]

I would set up HSRP for the single default gateway with redundancy.

Then I'd use the variance and max-paths commands in the eigrp setup. Variance will allow a greater FD to be used in the routing table, max-pathes will tell the router how many paths it can have to a destination.

Hope this helps.
Leigh

 

[robward]

Thank you all for your responses

bell1996
This is more or less what I have at the moment. Because of the admin overhead of 2 default gateways I'm looking at somehow creating
1) One gateway
2) Maximum bandwidth to remote site
3) Hardware and connectivity failover
All kit used is Cisco 2620
If you have any more ideas please let me know

Thanks

Rob

Narizz28
This looks interesting; I have seen the option to change the MAC address but always steered clear of it. Do you think it would cover my 3 objectives? If so is there any chance you could send me some sample config.

Thanks

Rob

LeighH
Please correct me if I'm wrong, but if I use HSRP won't one route always be in standby. Because I'm using 2 leased lines, I need to get the maximum bandwidth to the remote site to make it cost effective. I have to meet all 3 objectives at the top to make the change worthwhile; I already have 2 and 3. If you have anymore ideas please let me know.

Thanks

Rob

 

[gconnect]

I think Narizz28 has given you the best option being that you are dealing with 2 seperate devices..........

I wouldn't worry about the MAC issue. it's a virtual MAC address. Everything will be handled by ARP Resolution as far as communications from PC's are concerned.

"GLBP provides load balancing over multiple routers (gateways) using a single virtual IP address and multiple virtual MAC addresses. Each host is configured with the same virtual IP address, and all routers in the virtual router group participate in forwarding packets."

http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guide09186a00801541c8.html

-gC-

 

[Narizz28]

GC is correct, and both routers (or more) will keep their real MAC and IP addresses (so you can still VTY into a specific router).

The only question I have about GLBP isn't really about GLBP at all, but rather how often do devices like a PIX or other external device resolve the ARP and thus get a new Virtual MAC from the next ine the round robin team. I.E. How long will the PIX cache the resolution before polling again? That will determine how long it will send to that one router before looking up again and rolling to the next router. Not really a big deal in my scenarion as I have multiple devices in my perimeter, and each one's lookup will result in it using the next router in the team, but I am still curious...

 

[Narizz28]

*** The following is posted AS I UNDERSTAND IT and needs to be thouroughly researched before implementation ***

I guess I should've read the command reference before inquiring about the ARP cache timeout on a PIX. It appears that it's simply a matter of putting a line in like:

ARP TIMEOUT seconds

So if, in a PIX (or router), you want it repoll for the MAC address every 60 seconds, you'd add a line like:

ARP TIMEOUT 60

(In router IOS, this is done in the Interface Configuration)

The default is 14400 (4 hours). On a PIX, pay attention to ARP cache's you don't want to poll and that you want to be permanent. If your DMZ devices are static, consider adding permanent ARP entries for them (as well as the internal device the PIX is plugged in to, say the default gateway if the LAN is isolated from the PIX via it).

While administratively this can lead to more work, it might be worth it to cut down on a device continously polling for ARP resolution and increasing unwanted traffic.

Assuming that you'd have an interface on the same network as your GLBP team, in a router, you'd just configure that one interface's timeout to poll more often and rotate which team member it uses, while the others use their default timeout. On a PIX, it's a global config, and you'd want to control the ARP life of each device it touches if you don't want it constantly polling for all device's MAC addresses with the same timeout. You set a device's MAC permanently in PIX with:

ARP if_name ip_address mac_address alias

Without the alias tag, the ARP table entry will repoll at the end of the specified default timeout period (handy command in PIX when changing devices and you need an immediate MAC address replacement in the ARP table).

Anyone see any flaws with this method? I'm open to ideas.

Hope this helps..

 

[LeighH]

Howdy,

If you have 2 routes to somewhere and you were using eigrp, eigrp will put them both in it's topology table. It will use one and keep the other as standby.

If you use the variance command and the max-paths command, you can tell it to load balance over the two.

Hope this helps,
LH

 

[robward]

Thanks for all your replies; I'll research your suggestions and let you know how I get on.

Thanks again

Rob