Telnet resolving names via IPv6 instead of ipv4

[jaredkelsey]

If I ping tools.cisco.com it is successful via ipv4:

ROUTER# ping tools.cisco.com
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 173.37.145.8, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 62/62/63 ms

But if I try to telnet to tools.cisco.com port 443 I get an ipv6 name lookup! I'm not running ipv6 anywhere on this router:

ROUTER#telnet tools.cisco.com 443
Trying 2001:420:1101:5::A, 443 ...
% Destination unreachable; gateway or host down

ROUTER#

What the heck is going on?

--<snip> --
ip name-server <my internal dns ipv4 address>
ip domain lookup source-interface Loopback0
ip domain name <my internal domain name>

http client source interface Loopback0

interface Loopback0
ip address 10.255.0.136 255.255.255.255
end

[michel.prevost]

Got anygthing on this anyone?

[Georg Pauwen]

Hello,

I looked at some other posts, somebody suggests to configure:

call-home/http resolve-hostname ipv4-first

and explicitly disable (no ipv6 enable) on the interfaces.

[michel.prevost]

Hi Georg, 

I've already did all that. I also tried to change the server in the http url for the IP address of the server, but still stuck with the same error (205)

Thanks for your answer. Have a nice day. 

[Georg Pauwen]

Hello,

sorry for the late reply. I cannot TELNET to the site at all. What if you configure a host entry in your router:

ip host tools.cisco.com 173.37.145.8

I wonder if the site is up at all...

[prasant.kumar.samal]

please use below command to check 

telnet tools.cisco.com 443 /ipv4

you wll get correct result

also try below command

no service call-home

no call-home

service call-home

call-home

http resolve-hostname ipv4-first

[TelluR]

HI

telnet tools.cisco.com 23 /ipv4

Work on an old CSR 1000V.

[jamesbos96602]

it next impossable stop u first have block it on internet router, .

2 all computers ipv6 should be turn off now here probem with it with new updates i found no real way tunning it off , note route print, only one server should be listed firewall or gateway,  but if u look carefull i be willing bet there ip address in it u dont use,

in fack all them should be removed,  now oddly domains some what require this to work, now useing gpo u trun some this off, domains never used dns server that we can see use ipv6  so why use it, it registers to microsoft servers, so they track what u do, so trunning it off at router is must now u can use host file to ack as dns server  sadly wont update as needed, and this looks to be a internal interface 255, 255.255.255 used for only broadcast, and by way that not ipv6 address fe80::999b:f1c6:e45e:d7b7/128 that is ipv6 address ,   what u showing is broadcast address most likely set up for internal stystems needs

[Devaa]

Just in case if anyone still face this issue, just check if this helps. 

ip telnet source-interface Loopback 0

[vishalbhandari]

@jaredkelsey Your router is trying to resolve tools.cisco.com via IPv6 for the Telnet connection because modern DNS servers often return both IPv4 (A) and IPv6 (AAAA) records. Since your router doesn't have IPv6 configured, the connection fails when it attempts to use the IPv6 address. To resolve this, you can explicitly disable IPv6 DNS resolution on the router using the command:

"no ip domain lookup nsap"

This ensures the router only resolves and uses IPv4 addresses for connections like Telnet. Alternatively, you can specify the IPv4 address directly in your Telnet command.

[JustTakeTheFirstStep]

SW(config)#no ip domain lookup nsap
SW(config)#end
SW#telnet tools.cisco.com 443
Trying 2001:420:1201:5::A, 443 ... 
% Destination unreachable; gateway or host down