Because R1 and R2 are not connected to the same ISP, he has to change his IP address to use the other connection. (because he isn't using BGP to announce his netblock reachable through both connections). HSRP can't change his IP.
I've been thinking about it, and there is a (scrapped together junkyard-wars) way to make this work. You can HSRP the two routers and have the backup router NAT the other ISP's IP to a Ip that is valid for it's connection. This is a ugly solution, and only works for SMTP incoming mail transfers from other servers. (because of DNS's MX record priority feature). Another strike against it is if one of the links fails, all of the SMTP sessions in Progress will drop, and the remote (sending) mail server will have to re-initiate. ... Isp1 - Ip Range 1.1.1.0/28 (0-15) Isp2 - Ip Range 2.2.2.0/28 (0-15) Mail server is configured for the ip of 1.1.1.2, with a default Gateway of 1.1.1.1 Both routers are a member of an HSRP group and listen on 1.1.1.1 R1 is the HSRP primary, tracks the serial link, and preempts. R2 is the HSRP backup, and preempts if r1's serial link fails. R2's ethernet interface is IP nat inside, and the t1 interface is ip nat outside. R2 has a single static nat entry that translates 1.1.1.2 to 2.2.2.2.. ip nat inside source static 1.1.1.2 2.2.2.2 The DNS records are configured as follows domain.com. MX 10 1.1.1.2 domain.com. MX 20 2.2.2.2 Now, Looking at all of the above and understanding that this doesn't fix clients trying to connect to the server with POP3 or SMTP directly from outlook or eudora... Do you think this is a good solution? ... (no) BGP is the right answer to this customers needs. Sadly, I know someone is going to look at this and start pushing it to customers as a solution. -Ejay -----Original Message----- From: John Neiberger [mailto:[EMAIL PROTECTED]] Sent: Monday, February 25, 2002 2:51 PM To: [EMAIL PROTECTED]; [EMAIL PROTECTED] Subject: RE: TWO ISP AND ONE FAILURE [7:36371] I'm not sure I understand your point. Assume the following topology: [R1] [R2] | | | | \----------------------/ | [HOST] The two border routers are R1 and R2 and each have a connection to an ISP. HSRP is configured to track the WAN link. The default gateway on the host is the HSRP standby ip address. If either WAN link goes down, the relevant router--because it is tracking the WAN link--will notify the other router that it is no longer eligible and the other router will take over. Why are you saying that the perceived uptime to the host would not increase using this method? As I see it, unless both links go down, the downtime would be quite minimal. Thanks, John >>> "Hire, Ejay" 2/25/02 11:24:23 AM >>> Come on guys, Think about it for a minute. Do you really think the router is failing, or is his downtime caused by the wan link? HSRP won't significantly increase your uptime if the wan link is failing and he has to manually change his server's IP/default gateway to switch to the other link. A diferent way to think of it... If you had a car with no brakes and a broken tail-light, which would you fix first? -Ejay -----Original Message----- From: Ladrach, Daniel E. [mailto:[EMAIL PROTECTED]] Sent: Monday, February 25, 2002 11:48 AM To: [EMAIL PROTECTED] Subject: RE: TWO ISP AND ONE FAILURE [7:36371] Run HSRP between the two cisco routers and then point your default gateway to the VIP address. Daniel Ladrach CCNA, CCNP WorldCom -----Original Message----- From: Yassel Omar Izquierdo Souchay [mailto:[EMAIL PROTECTED]] Sent: Monday, February 25, 2002 10:11 AM To: [EMAIL PROTECTED] Subject: TWO ISP AND ONE FAILURE [7:36371] Hello i have a frecuent porblem with one of my isp, i have two cisco routers and each one to different isp. Frequentily i have to change the gateway of one of my servers, because one isp is failure. I want to know if with one of BGP, OSPF, RIP, NAT or other protocol i could do the change automatically to the other active isp. It happening me right now. And when i have to do that i have to reset one of my servers.. :S. Is a costs operatrion its a mail server. So if somebody knows how to resolve between routers with different isp each one, how to route accross the other good gateway. Thnx in advance Yassl Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=36428&t=36371 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
