The RSA host key has changed

[fredsem]

Hello Community,
I am testing vr-sros, so I created a docker image with vrnetlab successfully.

[root@host1 ~]# docker images
REPOSITORY         TAG        IMAGE ID       CREATED        SIZE
**vrnetlab/vr-sros   20.10.R1   cd2961ef3b68   3 hours ago    883MB**
ubuntu             20.04      fb52e22af1b0   7 days ago     72.8MB

I created the following yaml file and deployed the vr-sros successfully.

[root@host1 ~]# cat vr-sros-lab.yml 
name: vr01
topology:
  nodes:
    vr01:
      kind: vr-sros
      license: license.key
      type: "cpu=2 ram=4 slot=A chassis=VSR-I card=cpm-v mda/1=mda/1=m20-v"
      image: vrnetlab/vr-sros:20.10.R1
    vr02:
      kind: vr-sros
      license: license.key
      type: "cpu=2 ram=4 slot=A chassis=VSR-I card=cpm-v mda/1=mda/1=m20-v"
      image: vrnetlab/vr-sros:20.10.R1


[root@host1 ~]# containerlab inspect --all
+---+-----------------+----------+----------------+--------------+---------------------------+---------+-------+---------+-----------------+----------------------+
| # |    Topo Path    | Lab Name |      Name      | Container ID |           Image           |  Kind   | Group |  State  |  IPv4 Address   |     IPv6 Address     |
+---+-----------------+----------+----------------+--------------+---------------------------+---------+-------+---------+-----------------+----------------------+
| 1 | vr-sros-lab.yml | vr01     | clab-vr01-vr01 | f1abc2b93353 | vrnetlab/vr-sros:20.10.R1 | vr-sros |       | running | 172.20.20.10/24 | 2001:172:20:20::a/64 |
| 2 |                 |          | clab-vr01-vr02 | d2983e5f048c | vrnetlab/vr-sros:20.10.R1 | vr-sros |       | running | 172.20.20.3/24  | 2001:172:20:20::3/64 |

I destroyed the topology and deployed it again but adding some nodes.

[root@host1 ~]# containerlab deploy --topo vr-sros-lab.yml 
INFO[0000] Parsing & checking topology file: vr-sros-lab.yml 
INFO[0000] Creating lab directory: /root/clab-vr01      
INFO[0000] Creating docker network: Name='clab', IPv4Subnet='172.20.20.0/24', IPv6Subnet='2001:172:20:20::/64', MTU='1500' 
INFO[0000] Creating container: vr07                     
INFO[0000] Creating container: vr04                     
INFO[0000] Creating container: vr09                     
INFO[0000] Creating container: vr08                     
INFO[0000] Creating container: vr03                     
INFO[0000] Creating container: vr01                     
INFO[0000] Creating container: vr06                     
INFO[0000] Creating container: vr02                     
INFO[0000] Creating container: vr05                     
INFO[0010] Adding containerlab host entries to /etc/hosts file 
+---+----------------+--------------+---------------------------+---------+-------+---------+-----------------+----------------------+
| # |      Name      | Container ID |           Image           |  Kind   | Group |  State  |  IPv4 Address   |     IPv6 Address     |
+---+----------------+--------------+---------------------------+---------+-------+---------+-----------------+----------------------+
| 1 | clab-vr01-vr01 | 4a981fd96ca2 | vrnetlab/vr-sros:20.10.R1 | vr-sros |       | running | 172.20.20.3/24  | 2001:172:20:20::3/64 |
| 2 | clab-vr01-vr02 | 8568817ee519 | vrnetlab/vr-sros:20.10.R1 | vr-sros |       | running | 172.20.20.8/24  | 2001:172:20:20::8/64 |
| 3 | clab-vr01-vr03 | 648dec4adcbc | vrnetlab/vr-sros:20.10.R1 | vr-sros |       | running | 172.20.20.10/24 | 2001:172:20:20::a/64 |
| 4 | clab-vr01-vr04 | 78581cf5e275 | vrnetlab/vr-sros:20.10.R1 | vr-sros |       | running | 172.20.20.6/24  | 2001:172:20:20::6/64 |
| 5 | clab-vr01-vr05 | d061c4d943ba | vrnetlab/vr-sros:20.10.R1 | vr-sros |       | running | 172.20.20.2/24  | 2001:172:20:20::2/64 |
| 6 | clab-vr01-vr06 | cde6f08d0eb0 | vrnetlab/vr-sros:20.10.R1 | vr-sros |       | running | 172.20.20.9/24  | 2001:172:20:20::9/64 |
| 7 | clab-vr01-vr07 | f7fd25f640ab | vrnetlab/vr-sros:20.10.R1 | vr-sros |       | running | 172.20.20.4/24  | 2001:172:20:20::4/64 |
| 8 | clab-vr01-vr08 | 9ef2b3e4daca | vrnetlab/vr-sros:20.10.R1 | vr-sros |       | running | 172.20.20.7/24  | 2001:172:20:20::7/64 |
| 9 | clab-vr01-vr09 | 72b5fd60d55d | vrnetlab/vr-sros:20.10.R1 | vr-sros |       | running | 172.20.20.5/24  | 2001:172:20:20::5/64 |
+---+----------------+--------------+---------------------------+---------+-------+---------+-----------------+---------------------

Note, the IP address of nodes has changed, so when I try to connect to the old nodes (same names), I have an issue with RSA key.

[root@host1 ~]# ssh admin@clab-vr01-vr02
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@       WARNING: POSSIBLE DNS SPOOFING DETECTED!          @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
The RSA host key for clab-vr01-vr02 has changed,
and the key for the corresponding IP address 172.20.20.8
is unknown. This could either mean that
DNS SPOOFING is happening or the IP address for the host
and its host key have changed at the same time.
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that a host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
SHA256:WBB6T3+NlEWR66lvgUl5y7jDU/B+ia0vj1AA+9gU5pE.
Please contact your system administrator.
Add correct host key in /root/.ssh/known_hosts to get rid of this message.
Offending RSA key in /root/.ssh/known_hosts:4
RSA host key for clab-vr01-vr02 has changed and you have requested strict checking.
Host key verification failed.

The workaround is run the following command every time the topology is deployed.
rm -rf /root/.ssh/known_hosts

The question is, how can I avoid the issue with RSA Key when I try to connect via SSH to nodes re-deployed?.

Thanks for the comments.

[hellt]

Hi @fredsem
this behaviour is expected and has nothing to do with containerlab

you can create the ~/.ssh/config file with the following content to silence this warning

Host clab-*
  StrictHostKeyChecking no
  UserKnownHostsFile /dev/null