Allow Telnet ACL?

[andy_johnson(cnews)]

I wish to deny telnet on our network bar one machine is this possible using acl's

[Bruce Campbell_3 · Accepted solution]

Yes, it is possible with the 5400zl series
and some others.

To block inbound telnet to a vlan
except for machine a.b.c.d it would be:

ip access-list extended "block-telnet"
10 permit tcp 0.0.0.0 255.255.255.255 a.b.c.d 0.0.0.0 eq 23
20 deny tcp 0.0.0.0 255.255.255.255 0.0.0.0 255.255.255.255 eq 23
30 permit ip 0.0.0.0 255.255.255.255 0.0.0.0 255.255.255.255
exit

Assumes clients are on vlan numbered
'n'

vlan n
ip access-group "block-telnet" in
exit