Some food for thought:
Q1: Is the mail server and LANs default router the same box ?
A1: ---> no, mail server is redhat 9 and our routers ( gatewayes) are cisco
---> marks.
---> but i want use routing of mail-server for changing email direction on
link failover without any changing on gatewayes.
Q2: Are the interfaces for both primary and backup directly connected to
the same box ?
A2: --> yes, my mail server have 2 ethernet card each one connectes to it's
internet line.
Q3: Are both internet connections NATed ? or routed ?
A3: ---> no NAT
Q4: You need to confirm the reliability of the mechanism the router uses
to know when the primary Internet link has failed.
A4: ---> i use ping for failover checking of both lines.
Q5: If your requirement is as simplictic as wanting a backup to be used
only when the primary link fails, maybe setup two default routes in your
routing table with a lower metric on the primary route. In the event
the link goes down I presume the interface will also go into down state,
and therefore the routing entry will be removed implicitly by the
kernel. The backup route with the higher metric will then be selected
for default routing.
A5: --> i test this way, but wven the primary link failed, others didn't do
routing!
* Actually test the situation where your primary link fails and confirm
the host it's directly connected to can detect this and does bring that
interface down.
In the situation where the mail host and LANs default router is the same
box and the two Internet links are suppled on dedicated ethernet interfaces:
# Primary link via gateway 10.0.0.1 on eth0
route add -net default gw 10.0.0.1 dev eth0
# Backup link via gateway 10.0.1.1 on eth1
route add -net default gw 10.0.1.1 metric 1 dev eth1
Q6: One area to look at is how the default route is added when the backup
link comes up, this would usualy mean altering the configuration to how
the backup link add's its default route, you simply add the "metric 1"
into the route command at this point.
A6: ---> Have any other idea?
--> these works only enable sending emails.in other side, how i could recive
emails thru second link when first link is failover?
Thanks a lot,
masroor
--
IUT WebMail Service at CIS (https://cc.iut.ac.ir/webmail/)
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