Yes, however it is more complex than you might imagine.
One other thing is that I would check very carefully that the slots that you plan to use support the WICs. I was somewhat surprised that on the 2801 not all slots supported the T1 WIC (maybe E1?) that I randomly stuck in a slot and shipped the router off. Much head scratching.
THe 2801 has slot0 be a VIC only slot. The WIC-1DSU-T1-V2 should be able to go into any other slot than slot0. Could that be it? Likewise, a 2801 wouldn't be able to run 4 ADSL cards, but a 2811 and up should be able to.
But I don't think the setup is going to be very easy at all unless the ISP supports multilink PPP on ADSL.
I would like to use a Cisco 2800 router with 4 x ADSL cards to load share traffic to the Internet. The inside LAN would be a single /24 and the router the default gateway.
Assuming I have 4 x circuits (4 x separate public IP's), am I right in assuming that subject to 4 x default routes being in the routing table, the router will simply load share (using CEF) on a destination basis. I would then PAT the traffic to each of the 4 public IP's.
The only thing concerning me (subject to anyone else point out a flaw int the above) is how I fail traffic over from a connection that drops to one of the 3 x remaining connections.
Normally I would use a default route pointing out the dialer interface. In the event that the corresponding ATM interface goes down, the route would not disappear. Working on the assumption that 4 x links may share the same DSLAM I don't see how I can set a next hop address.
Assuming a Dialer interface is the way I guess the trick is to work out when the corresponding ATM went down. Alternatively use a virtual template ?
Does anyone have an opinion on whether this is possible.
Regards
Darren
I forget the exact card now, but it was for a full voice router, DSPs etc. After years of pretty much, it is fits it will work, it was a bit of a shock:)
I greatly applaud Cisco for making their stuff so easy to use. Mostly:) To those that say it is not, I recommend getting in a time machine, going back to 1998 and having a go with Cabletron, 3com, DEC, etc. No two bits of kit worked the same way, everything needed its own special console cable and magico dedicated special unique configuration software. I exagerate slighty perhaps.
I should have mentioned MPPP - however I have never actually used an ISP that did support MPPP on DSL:-(
The document that I listed earlier seems plausible, I have though not studied it in detail and as you say it is not exactly simple:)
This is normally not going to work, because in a setup like that the router will send traffic randomized to the 4 circuits independent of the source address, and the ISP will normally (or: hopefully) filter the traffic to prevent address spoofing. What you would want is the router setting up a NAT translation entry one time for each session, and then sticking to the particular ADSL circuit for that session's traffic. The initial selection of the circuit should somehow be balancing the traffic, and should skip circuits that are inoperative. I have tried to do this in the past, but was not very successfull. I used a loopback interface with policy routing to make the router select an outgoing interface based on source address of the traffic, but could not get a "traffic distribution" system working. So I used NAT acls to map ranges of internal addresses to external circuits. Not good balancing and not handling the case of a failed ADSL line. It looks like the OER mechanism could do what you want. Other manufacturers are selling specialized routers that handle this case out of the box with little or no configuration.
There are several ADSL2+ suppliers in the UK and ADSL2+ offers bonding natively so you don't have to worry about MLPPP. If I were you, I'd get two bonded circuits from one ISP and two from another and then load balance over them, to give yourself a bit more resilience. Obviously outbound load balancing is a lot easier than inbound in this kind of scenario.
Outbound load balancing easy? Is there no source address filtering on ADSL connections in the UK?
I assumed he was using NAT.
Sure, but AFAIK the NAT and load balancing functions in Cisco routers are independent of eachother. So when you have 4 outgoing lines and
4 default routes the outgoing traffic will be NATted to the 4 external IPs but the router will not stick to using the correct external IP on each line. Traffic with address of line 1 will be sent on lines 2-4 as well. Where they will be filtered when source address filtering is in use.It looks like the Optimized Edge Routing functionality is a solution for that problem, but it is complex. There exist some purpose-built routers from other manufacturers that were specially developed for the "multiple Internet connections to be used with failover and balancing in a NAT environment" problem, where everything works out of the box. Of course they are less flexible than a Cisco.
Bod43 posted this link elsethread:
I guess that's the tradeoff. You choose between a specialist box that's easy to get working, but difficult to do anything unusual with, or a generalist one that is a pain in the ass to get working, but can do anything you can program it to.
With regards to Requirement #2, "You need to identify specific hosts that can be reachable through only one of the ISP connections and cannot be available if that ISP connection is not available".
What's the need for specifying a host that's only reachable from via one ISP if the 'ip sla ...' specifies a source interface?
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