check your MTU settings with
user@computer:~$ tracepath -n www.cix.hr
1: 10.254.30.250 0.099ms pmtu 1500
1: 10.254.30.254 0.425ms
1: 10.254.30.254 0.405ms
2: 10.0.0.1 1.345ms
3: 18.104.22.168 4.111ms
4: 10.51.0.2 4.327ms
5: 10.50.0.74 192.967ms
6: 22.214.171.124 6.561ms asymm 7
7: 126.96.36.199 4.719ms asymm 10
8: 188.8.131.52 6.181ms asymm 9
9: 184.108.40.206 5.390ms asymm 10
10: 220.127.116.11 4.403ms reached
Resume: pmtu 1500 hops 10 back 54
3CDaemon. Download it here.
my customer is peering with 2 ISP’s and has configuration with 2 BGP routers mutually connected with iBGP.
routers are reciving full tables from ISP’s and has 4 byte AS (XXXXXX).
recently we noticed that BGP session between customer and ISP2 is constantly flapping each 3 minutes. logs didn’t show anything useful
%BGP-4-MSGDUMP: unsupported or mal-formatted message received from X.X.X.X
I searched cisco forums and tried to isolate problem by inserting hidden command “neighbor X.X.X.X dont-capability-negotiate”.
%BGP-3-NOTIFICATION: received from neighbor X.X.X.X active 2/2 (peer in wrong AS) 2 bytes 5BA0
by reading this article I assumed that ISP is announcing itself with wrong AS.
problem was finally solved by entering command in global configuration mode (and removing dont-capability-negotiate)
ip tcp mss 1440
To learn something more about TCP MSS go here.
easy tutorial @ thegeekstuff.
Nice howto for Cisco ASA and other network devices supported by rancid. for mikrotik router check this post.
program for scanning networks for NetBIOS name information
nice document on Cisco site
nice howto with screenshots at cisco support forums
atpitude install dhcp_probe
dhcp_probe -f -o /home/user/dhcp.pcap eth0
or search in vlans!
dhcp_probe -f -o /home/user/dhcp.pcap eth0 -Q <vlan-id>
works on maverick but not on natty? sound familiar? ubuntu screwed something up, but the solution is quite simple:
sudo add-apt-repository ppa:pmcenery/ppa
sudo aptitude update && sudo aptitude install gvfs ipheth-dkms ipheth-utils
works like a charm 🙂