Posted on 2009-04-22
Last Modified: 2013-11-30

I have a client who's email server is blocking mail coming from our public IPs, or seems to be--we have no other SMTP issues with anyone, and the server accepts mail from our other gateway (its NATed and the public address is not on any blacklist).

This must be resolved immediately, at least with a working temporary solution.

To do this, the only way i see is to accomplish this is route that clients traffic to the other gateway. However, we do not have enough bandwidth on that ISP to suffice for all the traffic of the client. So, it can only be the SMTP traffic, and only the SMTP to that particular problem server.

Currently out core switch is the gateway for all the VLANs, and static routes traffic to an ASA where it is NATed. VOIP traffic is parted at the core switch to a different router for NAT and routing on the other ISP link.

I'd like to separate all clients smtp the traffic at the core, and send it to the other router.

I guess this should look something like this:

access-list 180 permit tcp any host x.x.x.x eq smtp

route-map SMTP permit 10
     match ip 180
     set ip default next-hop <ip of router, not asa>

apply on interface:

int vl 12
     ip policy route-map smtp


Can I do PBR and static routing simultaneously? Should the above config work? I have this currently, but it is not. Please advise.
Question by:demetri08
    LVL 28

    Accepted Solution

    -Remove the "default" keyword from the policy map.

    Can I do PBR and static routing simultaneously?

    Should the above config work?
    -The above config should send SMTP traffic destined for x.x.x.x to the router.  What happens after that depends on the router, and whether it is configured properly to provide Internet access for private addresses.
    LVL 28

    Expert Comment


    Modify the access list to send all traffic with a destination of x.x.x.x to the router; then you can run traceroute, and various other tests.

    Author Comment

    thanks. i'll change the acl...

    i have tested it, and the traffic does go to the other router (though i have to enable some sort of dynamic routing to get the rout maps to work, correct?).

    anyway, the traffic is nated properly, but the smtp is not working still--with different symptoms. first, telnet smtp-server 25 does not get any srt of response now. second, wireshark shows pretty much only tcp retrans from the server back to the cleints.
    LVL 28

    Expert Comment

    "though i have to enable some sort of dynamic routing to get the rout maps to work, correct?"
    -No.  Once the policy is applied to the interface, the route map will take effect.  Note, however, that it will only apply to traffic entering that interface; it will not affect traffic entering other interfaces, or exiting the interface.

    Author Comment

    thanks again.

    i'm thinking perhaps i'm going down a path i don't need to be. lets say we don't stcik to my original should i get all the clients smtp traffic (to just that one server) out through a different gateway. or, are there any other solutions i'm not thinking of?

    LVL 28

    Expert Comment

    PBR is the right tool to use for that.

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