Kenneth, Just one question about this problem: Do you report any performance problems or latency on your system because of this issue? The reason why I am asking is that I hardly remember seeing that before. But I haven't noticed any problem. I've just realized that the lookup covers both IPv6 and IPv4. An other question would be which version of RedHat you are running on? Cheers, Si >-----Original Message----- >From: redhat-list-bounces@xxxxxxxxxx >[mailto:redhat-list-bounces@xxxxxxxxxx] On Behalf Of Kenneth Holter >Sent: Friday, March 20, 2009 8:18 AM >To: General Red Hat Linux discussion list >Subject: Re: Strange IPv6 DNS lookups > >Thanks for the advice. > >I've followed the steps you outlined below, but the problem >unfortunately >persists. I've learned that most packages on the system are >compiled with >IPv6 support, so from what I can tell this is what is usually >happening: > > 1. The client process (can be more or less whatever process >running on > the linux box) issues a AAAA DNS query for the FQDN * > server1.example-prod.com* > 2. The DNS server drops the package, so the linux box >iterates through > the "search" entries in /etc/resolv.conf, adding the >entries found here to > the FQDN. This results in the bizarre queries mentioned in >my first post. > 3. When AAAA record queries does not return a valid answer, >a normal A > query is made. This query returns the corret result. > >Say I have two entries in the "search" section of >/etc/resolv.conf, I will >end up with the linux box issuing 3 unsuccessful AAAA queries for every >successful A query. This causes a great amount of overhead on >the DNS server >(or the linux box if caching is used). > >I'm sure we're not the only ones having to deal with this issue, so any >advice on how to proceed will be greatly appreciated. > >Regards, >Kenneth > > > >On 3/11/09, Reber, Simon <simon.reber@xxxxxxxxx> wrote: > >> Hey Kenneth, >> >> Try to fully disable IPv6 while adding: >> >> alias net-pf-10 off >> alias ipv6 off >> >> to /etc/modprobe.conf and to /etc/sysconfig/network >> >> NETWORKING_IPV6=no >> >> This should probably solve the problem (at least IPv6 is turned off) >> >> Cheers, >> Si >> >> >-----Original Message----- >> >From: redhat-list-bounces@xxxxxxxxxx >> >[mailto:redhat-list-bounces@xxxxxxxxxx] On Behalf Of Kenneth Holter >> >Sent: Monday, March 09, 2009 4:17 PM >> >To: redhat-list@xxxxxxxxxx >> >Subject: Strange IPv6 DNS lookups >> > >> >Hello all. >> > >> > >> >Several of our RHEL-servers are issuing strange DNS lookups. >> >Consider this >> >example: >> > >> > >> >* 1 0.000000 1.2.3.4 -> 5.6.7.8 DNS Standard query AAAA ** >> >server1.example-prod.com* <http://server1.example-prod.com/>* >> > 9 0.007891 1.2.3.4 -> 5.6.7.8 DNS Standard query AAAA >> >server1.example-prod.com.example-test.local >> > 11 0.092904 1.2.3.4 -> 5.6.7.82 DNS Standard query A >> >server1.example-prod.com >> > 12 0.093356 5.6.7.8 -> 1.2.3.4 DNS Standard query >> >response A 1.2.3.4 >> >* >> > >> >>From what I can tell, the client first issues two IPv6 DNS >> >lookups, before >> >falling back to IPv4 lookup. We're not running IPv6 (and our >> >DNS servers do >> >not support IPv6 lookups), so the client is not getting and >> >answer before >> >issuing the IPv4 lookup. >> > >> >I've very puzzled by the second query, in which the FQDN of >> >the lookup query >> >is appended another domain. I've noticed that the appended >> >domain may be >> >both the same domain name (i.e. >> >server1.example-prod-com.example-prod.com) >> >or another domain as in the example above. >> >Does anyone have a clue as to why such bizarre queries are >> >performed by the >> >client? >> > >> >Since we're not running IPv6, I have simply disabled it for >this server >> >(grepping "lsmod" does not return any "ipv6" results). Yet >the problem >> >remains. Does the DNS lookup library automatically issue IPv6 >> >queries before >> >issuing IPv4 queries? Is there a way to disable IPv6 lookups? >> > >> > >> >Regards, >> >Kenneth Holter >> >-- >> >redhat-list mailing list >> >unsubscribe >mailto:redhat-list-request@xxxxxxxxxx?subject=unsubscribe >> >https://www.redhat.com/mailman/listinfo/redhat-list >> > >> >> -- >> redhat-list mailing list >> unsubscribe mailto:redhat-list-request@xxxxxxxxxx?subject=unsubscribe >> https://www.redhat.com/mailman/listinfo/redhat-list >> >-- >redhat-list mailing list >unsubscribe mailto:redhat-list-request@xxxxxxxxxx?subject=unsubscribe >https://www.redhat.com/mailman/listinfo/redhat-list > -- redhat-list mailing list unsubscribe mailto:redhat-list-request@xxxxxxxxxx?subject=unsubscribe https://www.redhat.com/mailman/listinfo/redhat-list
