Marek Skrobacki

Telnet to non-zero routing domain on the F5

Problem

Sometimes you may need to run a telnet to a server that is not on the default routing domain, but you are unable to do so because telnet does not support routing domains. Below is an example of such problem:

# telnet 192.168.3.4%10
telnet: 192.168.3.4%10: Name or service not known
192.168.3.4%10: No address associated with name

Solution

There is a workaround that allows you to use programs that support IPv6 to resolve your problem. It turns out there is a way to translate IPv4 and routing domain id into a IPv6 address. Following method is used to convert:

  • convert your routing domain ID to hex. In our case routing domain 10 will be converted to a

  • convert each of the IPv4 octets to hex. 192 becomes c0, 168 becomes a8, 3 becomes ”’03”’, and 4 becomes … 04

Then use following IPv6 address:

2620:0000:0C10:F501:0000:Route Domain ID:IPv4 IP upper 2 bytes:IPv4 IP lower 2 bytes

In our example, 192.168.3.4%10 will be converted to 2620:0000:0C10:F501:0000:a:c0a8:0304

# telnet 2620:0000:0C10:F501:0000:a:c0a8:0304 80
Trying 2620:0000:0C10:F501:0000:a:c0a8:0304...
Connected to 2620:0000:0C10:F501:0000:000a:c0a8:0304 (2620:0000:0C10:F501:0000:a:c0a8:0304).
Escape character is '^]'.

Bug in BigIP versions earlier than 10.1.0

You may hit the bug when this does not work. If the version is earlier than 10.1.0 you will have to use 2610 instead of 2620 during conversion.

Routing Domains F5 Telnet Ipv4 Ipv6