Skip to main content

Cisco ASA 5505 and EDNS issue

resolution: update your running config on your firewall. See below

issue:
I changed my primary internal DNS to run on a RHEL 6.2 system. After that there were noticeable lags occasionally when I would browse.  Upon review of the syslog I noticed messages like the following;

Jan 31 22:44:41 zion named[26381]: success resolving 'p03-bookmarks.icloud.com/A' (in 'icloud.com'?) after reducing the advertised EDNS UDP packet size to 512 octets

I happen to use a Cisco ASA 5505 and I did some digging around.

firewall(config)# show run | grep mess
  message-length maximum 512

So - it turns out the value is set as part of a policy-map.  Let's tune it.


firewall(config)# policy-map type inspect dns preset_dns_map
firewall(config-pmap)# parameters
firewall(config-pmap-p)# no message-length maximum 512
firewall(config-pmap-p)# message-length maximum 4096
firewall(config-pmap-p)# 
firewall(config-pmap-p)# write mem
Building configuration...
Cryptochecksum: 3a1cdf20 91ce7d1e d8b188fc 1ac006fb 


4215 bytes copied in 1.420 secs (4215 bytes/sec)
[OK]
firewall(config-pmap-p)# 

Everything is better... now I just get these errors (and nothing on my side will fix this issue)
Jan 31 22:46:30 zion named[26381]: error (network unreachable) resolving 'thumbnail.newsinc.com/A/IN': 2001:500:90:1::18#53


Labels:

Comments

Post a Comment

Popular posts from this blog

P2V using dd for KVM-QEMU guest

Preface: I have certainly not exhaustively tested this process.  I had a specific need and found a specific solution that worked. Situation:  I was issued a shiny new laptop running Red Hat Enterprise Linux 7 (with Corp VPN, certs, Authentication configuration, etc...)  The image was great, but I needed more flexibility on my bare metal.  So, my goal was to P2V the corporate image so I could just run it as a VM. * Remove corporate drive and install new SSD * install corp drive in external USB-3 case * Install RHEL 7 on new SSD * dd old drive to a disk-image file in a temp location which will be an image which is the same size as your actual drive (unless you have enough space in your destination to contain a temp and converted image) * convert the raw disk-image to a qcow file while pushing it to the final location - this step should reduce the disk size - however, I believe it will only reduce/collapse zero-byte blocks (not just free space - i.e. if you delete a file, it may
1 comment
Read more

RHN Satellite Server (spacewalk) repomd.xml not found

"repomd.xml not found" If you add a channel, or if your RHN cache gets corrupted, and one of your guests complains that it cannot find repomd.xml for jb-ews-2-x86_64-server-5-rpm (for example) - you need to rebuild your repodata cache. Normally this is an automated job - which is exemplified by the fact that you have obviously built out your entire Satellite environment and never had to do any of the steps you are about to do. So - some prep work: Open 3 terminals to your Satellite Server and run: # Term 1 cd /var/cache/rhn watch "ls -l | wc -l" # Term 2 pwd cd /var/log/rhn tail -f rhn_taskomatic_daemon.log # Term 3 satellite-sync --channel=jb-ews-2-x86_64-server-5-rpm Once the satellite-sync has completed, you >should< see the count increment by one.  If you are unlucky (like me) you will not. You then need to login to the Satellite WebUI as the satellite admin user. Click on the Admin tab (at the top) Task Schedules (on the left) fin
Post a Comment
Read more

Extending SNMP to run arbitrary shell script

Why are we here... This is not likely something I would have pursued under normal circumstances.  I happen to be working for a customer/client who is not afforded a lot of flexibility to accomplish their goals.  In this case, the rigor is justified.  They have to sometimes be fairly creative with how they solve problems. In this case they would like to utilize an existing snmp implementation to execute a command (or shell script) on a remote system.  They came to me with the idea of using Net-SNMP extend. https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Deployment_Guide/sect-System_Monitoring_Tools-Net-SNMP-Extending.html NOTE:  This is NOT a good implementation strategy in the "real world"  it will simply allow you to test the functionality.  There are a TON of security implications which would need to be taken in to consideration. Implementation Steps: [root@rh7tst01 ~]# yum -y install net-snmp net-snmp-utils [root@rh7tst01 ~]# cd /
Post a Comment
Read more