Weird problem. We have a collection of servers running CentOS 5 on EC2. The setup includes two DNS servers and two LDAP servers. DNS has a CNAME pointing at the primary LDAP server.
One machine (and only one machine) is giving me problems. I can ssh into the server using LDAP authentication. But once I'm on the machine, ping won't resolve the LDAP host even though DNS seems to work fine.
$ ping ldap.mycompany.ec2 ping: unknown host ldap.mycompany.ec2
Here's the output of dig:
$ dig ldap.mycompany.ec2 ; <<>> DiG 9.3.6-P1-RedHat-9.3.6-4.P1.el5_5.3 <<>> ldap.studyblue.ec2 ;; global options: printcmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 2893 ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;ldap.mycompany.ec2. IN A ;; ANSWER SECTION: ldap.mycompany.ec2. 3600 IN CNAME ec2-hostname.compute-1.amazonaws.com. ec2-hostname.compute-1.amazonaws.com. 55 IN A aaa.bbb.ccc.ddd ;; Query time: 12 msec ;; SERVER: 10.32.159.xxx#53(10.32.159.xxx) ;; WHEN: Tue May 31 11:16:30 2011 ;; MSG SIZE rcvd: 107
And here is resolv.conf:
$ cat /etc/resolv.conf search mycompany.ec2 nameserver 10.32.159.xxx nameserver 10.244.19.yyy
And here is my hosts file:
$ cat /etc/hosts 10.122.15.zzz bamboo4 bamboo4.mycompany.ec2 127.0.0.1 localhost localhost.localdomain
And here's nsswitch.conf
$ cat /etc/nsswitch.conf passwd: files ldap shadow: files ldap group: files ldap sudoers: ldap files hosts: files dns bootparams: nisplus [NOTFOUND=return] files ethers: files netmasks: files networks: files protocols: files rpc: files services: files netgroup: files ldap publickey: nisplus automount: files ldap aliases: files nisplus
So DNS works the way I would expect. And I can ping the ldap server by ip address. And I can even access the box with SSH using LDAP authentication.