T1 Redundancy

[sohtnax]

I currently have 1 T1 connecting to a 2600 Series Cisco Router. I would like to add another T1 from another service provider for redundancy and possibly either load balancing or for segration fo internal traffic and client traffic to our internet site. I have an extra router on hand. How would I go about doing this?

 

[gaveeve]

I wonder if HSRP might be an option for you. Basically that gives you a virtual gateway that has two or more actual gateways underneath it. HSRP automatically switches over if your active one fails. Load balancing is done with vlan segregation of your network. Its not the easiest. Here's a link

http://www.cisco.com/univercd/cc/td/doc/cisintwk/ics/cs009.htm

 

[routerman]

HSRP wont offer any support for load sharing, but a recent IOS addition could help, have a look at GLBP. If the T1 links are both carrying internal traffic and you have control of both ends then this could be done using EIGRP or OSPF.

HSRP provides a virtual gateway address that `floats' between 2 routers on the same LAN. if the primary fails the secondary takes over, and accepts traffic to be forwarded down the attached T1.

GLBP is useful where you have several host's on a LAN and you want to provide a degree of load sharing as well as a virtual gateway.

 

[hsh2hsh]

Why not take advantage of Route Map ?

Simon Yu
CCNP

 

[baddos]

Do you need redundancy for inbound or outound or both? If you only need redundancy for outbound (inet browsing, etc.) then the above would work good. If you have a large subnet (/24 or bigger), that you want announced to both ISPs, then you'll need to look into BGP.

 

[sohtnax]

My goal for this second T1 will not be for outbound internet brwosing, but instead to ensure that our web servers are accesible if one of the service providers goes down. In this case what would you suggest?

 

[tbilan]

If you want your web server accessible from both providers you'll need to make sure your 2nd provider can announce the IPs that are assigned to your web server. Technically this doesn't require you to run BGP but they will need to advertise your IPs via their BGP to the backbone.

You can add the second T1 to your existing router with no problems as long as you don't plan on running BGP with full routes on a 2600.

Whatever you do make sure before you sign anything with a second provider that they understand that your need is to have your web server accessible via their T1.



Tom Bilan
TJBA, Inc.
CCNP, CCDP, MCSE & CNE

 

[sohtnax]

Tom, thanks for your respone. The ISP seems to be clueless though. Every time I ask them to do this, they reply to me saying that "it will be a standard T1. How I choose to use it is my business" They seem to be avoiding the question, and unfortuantely I have already signed the paperwork. My experience with ISP's is somewhat limited, so any advice you can offer would be helpful.

Thanks.

 

[tschouten]

I would say call them up and ask to talk to their technical staff regarding routing. Most likely you are getting some representitive that doesn't even know what you are asking. Or you just happend to land yourself with a crappy ISP. Still, you should ask to talk with whomever handles routing and route manipulation. Or ask to talk to someone above whom you are talking with at the present time. tbilan is right though, all you need is in your case is those ip addresses of the web servers broadcast out both sides.

 

[tbilan]

I've dealt with some really stupid ISPs before. Treat them like 2 year olds and ask them to type 'tracert

http://www.whatever.com'

and watch it go 20 hops through the internet to your web server and then ask them why that is. They'll call you back in about a week after they call someone who understands routing.

Tom


Tom Bilan
TJBA, Inc.
CCNP, CCDP, MCSE & CNE

 

[sohtnax]

The same person who had no clue what I was asking for is now telling me that he will build his config to load in the ip addresses from my existing ISP into his own routing config. Therefore, when the T is turned up, it will load the block he is assigning me as well as those IP from my primary service provider, assuming they are portable. Does this sound right?

Will I have any conflicts if my secondary ISP routes the range of IP that my primary ISP has assigned (which I am
currenltly using for my web servers)?

 

[tbilan]

Sure as long as his routing config includes a BGP update to his upstream provider and that provider in turn updates their access-list to accept your addresses. Your block has to be at least a /24 (class C) or it will be filtered out by the peering points and thus useless.

You won't have any conflicts but you should realize that depending on how your addresses are advertised you may see all your internet traffic switch to your second provider and your main provider's link go unutilized.

I don't know your business but if your web presence is critical you may want to get a consultant who can work with the ISPs to get things done to meet your needs and not theirs. To find someone local go to:

http://tools.cisco.com/WWChannels/LOCATR/jsp/partner_locator.jsp

. Look for a Premier, Silver or Gold reseller because they're required to have CCNPs/CCIEs.


Tom Bilan
TJBA, Inc.
CCNP, CCDP, MCSE & CNE

 

[sohtnax]

When you say all my traffic, you mean only traffic to the ip addresses I ask him to advertise, correct? It really doesn't matter to me if all my traffic goes over either of the ISP's, so long as when one goes down the other takes over.

 

[tbilan]

You can't advertise 1 address, the minimum is 256. (255.255.255.0 or /24)

If set up correctly you should be able to pull a plug on a T1 and within seconds people on the Internet should be able to get to you through the other side.


Tom Bilan
TJBA, Inc.
CCNP, CCDP, MCSE & CNE

 

[nyy1023]

Actually Tom within the confederate network in each ISP you can advertise any size block you want. In order for all ISP's to hear the announcement you need to advertise nothing smaller than a /24 which in turn will be announced ina larger class by the ISP, often times but not allways. From what I am hearing about web traffic and not browsing traffic, I would set up BGP for only the web hosting traffic. The static route for the browsing will be prefered, and if they wanted to set it up with BGP as well in case the connection goes down they can do that and static will be prefered because of the routing metric.

Did I confuse anyone, besides myself?!?! geesh time for a nap!

 

[NetEng631]

The size of the blocks do not matter as much as having your own portable address space. You can advertize anything you want to your ISP it doesn't mean your ISP or the tier 1 ISP's will advertise this.
If your connecting to two different ISP you need BGP, Unless your using a floating static or something like that.

****Some questions to ask ****

Do you have your portable ARIN IP block that can be advertised to two different service providers or did you get these addresses from your current ISP?

Is your current ISP exporting your routes?
Is your current ISP supernetting your routes?
Does your router have enough power and memory. How many routes will you be recieving from your ISP.

Connecting to two ISP is not easy.