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Beginner

SMTP traffic fails when going out and back in the same Router

We have a customer using a 2911 router with 3 x DSL WAN links.

The customer runs a building with shared office space which people rent.

Customers in the building are experiencing a problem where they cant email other tenants i.e...

One tenants exchange server tries to make a connection to another tenants server by going out to the internet and back in via the same interface.

I believe this might be called "Hair Pinning"

I have attached the router config if anyone can help?

4 REPLIES 4
Contributor

Re: SMTP traffic fails when going out and back in the same Route

Since you don't appear to be blocking vlan-to-vlan traffic, why not ask each exchange admin to simply put an entry in the hosts file to point to the other exchange server so it will resolve to an internal address rather than an external.

Sent from Cisco Technical Support iPad App

Beginner

Re: SMTP traffic fails when going out and back in the same Route

I thought about that until we discovered some customers use Apple email servers

Contributor

Re: SMTP traffic fails when going out and back in the same Route

Apple email servers don't use Dns?

Sent from Cisco Technical Support iPad App

Beginner

Re: SMTP traffic fails when going out and back in the same Route

I should image so or they wouldnt get very far resolving names.

the difficult part of this is we just control the router all the servers are controlled by the individual customers within the building, asking them to create DNS records is likely to be an impossible task, i was hoping hair pinning would solve the issue

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