[j-nsp] MTU issue between juniper routers

[meryem Z]

Hi Pekka,

I checked this , but there are no dropped packets by the loopback filter policers :


show firewall filter protect-RE    

Filter: protect-RE                                             
Counters:
Name                                                Bytes              Packets
bgp-traffic                                        145288                 2993
ftp-traffic                                             0                    0
icmp-traffic                                   1800603780             62102280
junoscop-traffic                                       60                    1
others                                          563402042              7809827
snmp-traffic                                    637288880              6015830
ssh-traffic                                           928                   19
tcp-established                                3093764378             15322802
tcp-syn                                            831652                17062
telnet-traffic                                      17444                  308
traceroute-traffic                                  98549                 2359
vrrp-traffic                                            0                    0
Policers:
Name                                              Packets 
RE-HIGH-POLICER-ftp                                     0
RE-HIGH-POLICER-ssh                                     0
RE-HIGH-POLICER-vrrp                                    0
RE-LOW-POLICER-tcp-syn-attack-protection                    0
RE-MEDIUM-HIGH-POLICER-ntp                              0
RE-MEDIUM-HIGH-POLICER-snmp                             1
RE-MEDIUM-LOW-POLICER-telnet                            0
RE-MEDIUM-LOW-POLICER-traceroute                        0


Thanks.


> Date: Mon, 28 Mar 2011 08:38:18 +0300
> From: pekkas at netcore.fi
> To: meryem_z at hotmail.com
> CC: juniper-nsp at puck.nether.net
> Subject: Re: [j-nsp] MTU issue between juniper routers
> 
> On Fri, 25 Mar 2011, meryem Z wrote:
> > - MTU on Ge interface is configured to 4484 on both ends of the links. but ping (from P to PE ) greater than 1600 bytes fails.
> > - I checked interfaces configuration , and also did a "show interfaces" to verify the effective mtu value used. everything is ok.
> > - i'm suspecting some node on the transmission path between the P and the PE configured with the default value of 1500 for GE , but i couldn't find any equivalent command to the linux tracepath on juniper routers.
> 
> This is not very probable but:
> 
> Check that the packets are not being sent as fragments and dropped 
> in receiver's loopback filters.
> 
> Even though MTU is high, we've come across unnecessary (IPv6) 
> fragmentation when certain conditions are met - PR/571596
> 
> -- 
> Pekka Savola                 "You each name yourselves king, yet the
> Netcore Oy                    kingdom bleeds."
> Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings