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Xylene_UK_11374's avatar
Xylene_UK_11374
Icon for Nimbostratus rankNimbostratus
May 27, 2009

LTM9.4.6:- snat pool with 2 ISP links question

I would like to know how to set up the following:-

 

 

backend servers are mail relays / servers who make many DNS lookups, so many that the normal snat automap exhausts all ports.

 

 

I have2 links (isps available)

 

 

So my plan is to create a new virtual server on an internal IP address.

 

This vip will have a pool with a single member, the external DNS server (reachable via both isp links)

 

and then create a snat pool on the virtual which will have 2 IP addresses from each of the 2 subnets / links

 

 

Now the question is once the client IP has been snatted with one of the pool members, how does it know how to route out to the correct link?????

 

 

It will use the default gateway pool, but will it be 50 / 50 on getting the right gateway ???

 

 

 

DNS_VIP_UDP

 

10.159.144.120:53

 

protocol: UDP

 

protocol profile: udp_gtm_dns

 

SNAT_pool: DNS_SNAT

 

default pool: DNS_POOL

 

 

DNS_VIP_TCP

 

10.159.144.120:53

 

protocol: TCP

 

protocol profile: tcp_gtm_dns

 

SNAT_pool: DNS_SNAT

 

default pool: DNS_POOL

 

 

 

DNS_POOL

 

members: x.y.4.12:53

 

 

DNS_SNAT

 

4.xx.218.220

 

4.xx.218.221

 

12.yy.149.20

 

12.yy.149.21

 

-------------

 

My current routes has a default to a pool with the two ISP router IP.

 

4.xx.21.132 and 12.yy.149.4

 

 

 

Anyone give me a clue how to work around this with a rule or have any other idea's

 

 

Thanks

 

 

Xyleneuk
application delivery
dev
devops
iRules

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  • c_p_i_o_17707's avatar
    c_p_i_o_17707
    Historic F5 Account
    Jun 02, 2009
    Hello Bobcox,

     

    You're right you can not change the default UDP timeout for autosnat.

     

    For snat pool members (or individual explicitly defined SNATS), you can lower the tcp/udp/ip idle timeout for each address as follows in your bigip.conf

     

    snatpool my_snat_pool {

     

    members 1.1.1.1

     

    }

     

    snat translation 1.1.1.1 {

     

    tcp timeout 300

     

    udp timeout 300

     

    ip timeout 300

     

    }

     

     

    You can also do this from the GUI by going to:

     

    a) SNATS -> SNAT Translation List page in 9.4.x and clicking on each defined address OR

     

    b) In 10.x going to SNATS -> SNAT Translations dropdown directly and clicking on each defined address.

     

     

    HTH