Ping Unknown Host on CentOS at EC2
- by organicveggie
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.
Here's ping:
$ 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.
Any suggestions?
