[j-nsp] Doing SNAT only for destinations learned from a specific BGP peering

[Martin Tonusoo]

Hi Emmanuel,

> - MX204 does not support PAT at all
> - PAT is doable by offloading the work to a Linux box
> - SNAT + PAT is not doable elegantly on a sole MX204 box

That's correct. PAT is not doable on MX204.


> - MX204 does not support SNAT on interface (could have been the elegant configuration)
> - SNAT is doable with routing instances

MX204 supports one-to-one translation of IP addresses. For example,
following SNAT configuration is supported on MX204:

root at mx> show configuration services nat
pool 1-to-1-snat-pool {
    address 195.7.9.0/24;
}
rule 1-to-1-snat {
    match-direction output;
    term snat {
        from {
            source-address {
                10.23.44.0/24;
            }
        }
        then {
            translated {
                source-pool 1-to-1-snat-pool;
                translation-type {
                    basic-nat44;
                }
            }
        }
    }
}

root at mx>

This will map 10.23.44.1 to 195.7.9.1, 10.23.44.2 to 195.7.9.2, etc.
The address pool must contain equal or more addresses than the
source-address network specified under the from clause.

This kind of SNAT is performed directly within the Trio lookup block
and should offer near line-rate performance with very little and
stable latency.


> And thanks Martin for the time you put in writing your thorough and
> detailed example.

No problem at all.


Martin