CISCO- TWO ISP fail-over (No BGP)? <<HELP>>

Posted on 2007-10-07
Last Modified: 2013-12-14
I trying to figure out a way to configure this, here is what am trying to do- configure a redundant  link to the internet with two different ISPs with no BGP. Also, there will be a mail-server, and a few other public services on the LAN. Any ideas?
2x  2801 router (3x Ethernet Interfaces)
1x /30 Public IP Address
5x /29 Public IP Addrss
Charter  Cable Modem ISP-
1x /30 Public IP Address
5x /29 Public IP Address

Question by:svonwinkle
    LVL 11

    Expert Comment

    It would be hard to use public IP LAN addresses.
    You need to use NAT and assign two default routes. Assign higher metrica to the secondary and lower to primary.
    DynDNS record for your servers, it will change IP for your servers as needed.
    Round-robin DNS record which will return  IPs in different order for each request for load balansing.

    Need more details, let me know.
    LVL 57

    Expert Comment

    You can't have real inbound fail over without AS and BGP.  With dynamic DNS it may work, but not always.

    The problem is that you can't route ISP1 IP addresses over ISP2's network, or the other way around without AS and BGP.

    This means that for "mailserver.yourdomain.tdl" you need to have an IP address from both ISP1 and ISP2.  With round robin DNS you will load balance the inbound connections, but if ISP1 goes down, then every other request will fail.

    With dynamic DNS you could remove the entry for ISP1, but you have the issue of cached resolution requests.  Even if you code a ttl of 0, there are caching DNS servers on the internet that will cache entries for up to 72 hours no matter what ttl you code.

    So for inbound traffic, there is not a whole lot you can do.

    LVL 11

    Expert Comment

    giltjr, I'm agree.

    Besides that I'd purchase some sort of hosting for mail and other services from a reliable data center if it's mission critical for the business. Virtual dedicated servers are not that expensive this days.
    LVL 79

    Accepted Solution

    Do you have anything inside your routers, like a firewall?
    The issue is where/how you are going to do NAT and how to map 2 different public ip's to the same internal server.
    The fact that you have 2 routers makes is a little more feasible, but also more difficult to configure. Basically, setup SLA monitor on each router, advertise default routes to each other (OSPF or BGP), run HSRP or GLBP on the inside.

    It is not a simple task that can be accomplished in a forum like this. It takes meticulous planning and testing before putting into production mode. Highly suggest hiring a professional to come onsite to help you.
    LVL 11

    Expert Comment

    lrmoore, could you explain what's the poing to use SLA?

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