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New Member

Fault tolerant setup

Hi eveybody,

I have this project to implement which is very urgent. I need to setup two cisco routers( 800 series)connecting to two cisco switches(2950). The two cisco switches will be connected to by a crossover cable on the 100baseTX port. Two cat 5 cables now connects ports 1x on each of the cisco switches to two ports on a media converter/fault tolerant device(MDI/MDIX). The only port on the other end of the converter connectes to the (RJ 45 port) at the back of the server. The whole essence of this media converter is to (1) convert the 100TX connection into 100Fx and (2) To be able to provide connection fron the WAN connection through the router to the host Via the switches in case one of the switches developed fault. The point is to achieve high availability through the second port on the media converter if the first goes down. How do I achieve this stuff using cisco router 800 and cisco switch 2950. I have itemise the steps as follows:

Router(two) connects cisco switch(2950), 2950 connected with crossed cable on 100baseTx port, two 2950 connects using ports 1x to two port on the media converter, One port on the other end of the converter connects to The server(host) .

The point is, If One of the routers fail, the second can still route packet through via the port its corresponding switche is connected to on the media converter to the Host. This is what I want to achieve. I need your assistance

Thanks

6 REPLIES
Silver

Re: Fault tolerant setup

Near as I can tell, you have a classic high cost, low availability redundant setup. For redundant components to improve network availability (rather than just introducing more parts which can fail) three properties must be present:

1 - the ability to detect a failed component

2 - the ability to use an alternate component

3 - the ability to ensure the alternate will work when needed

In the scenario you describe, and interpolating the use of low cost DSL or Cable internet access, I don't see you having a way to do any of the three prerequisites unless your "media convertor" also has a means of detecting when one of your 800 routers loses connectivity to your ISP and can send all traffic to the other.

There is little the routers or switches can do to help you in this respect. Routers do not include the ability to shut down a switch's Ethernet port when the router detects a failure, nor do the 800 routers include the ability to detect most ISP access failures other than loss of link to the local DSLAM.

Good luck... if you've promised the boss higher availability, you're going to need it.

Vincent C Jones

www.networkingunlimited.com

New Member

Re: Fault tolerant setup

Dear VCJones,

You are the first person to reply my mail. I cannot but thank you for the time taken to read, understand and reply this mail. It shows that there are people out there interested in developing others with their skill base.

However, what do you suggest based on what I want to achieve and how do I go about acheiving this?

I have never been tired of moving from the known to the unknown so far I get the desired result.

Thanks once again for your professional advice

I am awaiting your quick response

regards

Silver

Re: Fault tolerant setup

First, my apologies for such a negative initial response. Although I fear the reason for the lack of responses to your posting is the hopelessness of the situation as you have described it.

On the positive side, a few suggestions:

1 - Set proper expectations with management. This project as you describe it (hopefully, there is information missing) is not going to improve availability of the Internet connection. If you were not the one to recommend this solution in the first place, distance yourself from responsibility for it as quickly as possible.

2 - Look for how to achieve requirement #1 in my original posting. Perhaps you can get the application being supported to detect when it can't reach the Internet through one of the routers, or you can run another application on the box which does the checking by pinging several well known destinations?

Or maybe you can convince your ISP to exchange routing packets with your 800 router? The 800 series does not support much, but probably at least supports RIP. If the router detects ISP failure, it could route outgoing packets to the other 800 router.

3 - Once you have a mechanism to detect failure, look

for a mechanism to compensate for failure. For example, if the application detects loss of a path, it could change the default gateway used for outgoing packets to use the alternate 800 router. Keep in mind that for communications to work, the alternate path must be selected for both incoming and outgoing packets. This may be automatic if using NAT.

4 - Once you have requirements #1 and #2 in place and working, put in place procedures to monitor the state of both paths, and routinely test the backup path if it is only used "on demand." Otherwise, you're setting yourself up for some ugly future surprises.

5 - Other solutions may be possible, there is way too much unspecified, and pulling all the pieces together could be a significant project, and well beyond the scope of "free sample" consulting. A couple of evenings curled up with my book (High Avaialability Networking with Cisco, out of print but widely available from "used" book dealers) will give you a better feel of all the things that can go wrong, and the myriad ways to deal with them. If the application is important, consider getting professional help.

Good luck and have fun! Two other hints... fix your posting process so you only post one response instead of four:-) and consider posting your questions in a forum more suitable to the topic being asked. I don't see any mention of virtual private network or IPsec in any of your descriptions.

Vincent C Jones

www.networkingunlimited.com

New Member

Re: Fault tolerant setup

Dear VCJones,

You are the first person to reply my mail. I cannot but thank you for the time taken to read, understand and reply this mail. It shows that there are people out there interested in developing others with their skill base.

However, what do you suggest based on what I want to achieve and how do I go about acheiving this?

I have never been tired of moving from the known to the unknown so far I get the desired result.

Thanks once again for your professional advice

I am awaiting your quick response

regards

New Member

Re: Fault tolerant setup

Dear VCJones,

You are the first person to reply my mail. I cannot but thank you for the time taken to read, understand and reply this mail. It shows that there are people out there interested in developing others with their skill base.

However, what do you suggest based on what I want to achieve and how do I go about acheiving this?

I have never been tired of moving from the known to the unknown so far I get the desired result.

Thanks once again for your professional advice

I am awaiting your quick response

regards

New Member

Re: Fault tolerant setup

Dear VCJones,

You are the first person to reply my mail. I cannot but thank you for the time taken to read, understand and reply this mail. It shows that there are people out there interested in developing others with their skill base.

However, what do you suggest based on what I want to achieve and how do I go about acheiving this?

I have never been tired of moving from the known to the unknown so far I get the desired result.

Thanks once again for your professional advice

I am awaiting your quick response

regards

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