[Bridge] Neighbour table overflow

Stephen Hemminger shemminger at osdl.org
Thu Jan 6 13:56:28 PST 2005


On Wed, 05 Jan 2005 22:10:48 +0800
ro0ot <ro0ot at phreaker.net> wrote:

> Based on the result of the command "brctl showstp br0" below, what is 
> the "designated bridge" means?

It means the the next step up the hierarchal spanning tree
from this bridge.  I.e where to send frames that aren't in the
bridge forwarding table 


> 
> Something strange on this line "designated bridge      
> 8000.000e6ae78720", this is because this is the MAC address of my 3Com 
> 4400 switch which I have VLAN running and bridge too...

Many switches use the same spanning tree protocol because they are
really just bridges. The issue is they assume that any other bridge
also sees all the traffic (and is not just on the VLAN).

You could try turning off STP but it might not help.


> Will this cause the problem?
> 
> root at fw01:~# brctl showstp br0
> br0
>  bridge id              8000.000c4120c1a6
>  designated root        8000.000bac2851c0
>  root port                 2                    path cost                136
>  max age                  20.00                 bridge max 
> age            20.00
>  hello time                2.00                 bridge hello 
> time          2.00
>  forward delay            15.00                 bridge forward 
> delay      15.00
>  ageing time             300.00
>  hello timer               0.00                 tcn 
> timer                  0.00
>  topology change timer     0.00                 gc 
> timer                   0.90
>  flags
> 
> 
> eth0 (1)
>  port id                8001                    state                
> forwarding
>  designated root        8000.000bac2851c0       path cost                100
>  designated bridge      8000.000c4120c1a6       message age 
> timer          0.00
>  designated port        8001                    forward delay 
> timer        0.00
>  designated cost         136                    hold 
> timer                 0.00
>  flags
> 
> eth5 (2)
>  port id                8002                    state                
> forwarding
>  designated root        8000.000bac2851c0       path cost                100
>  designated bridge      8000.000e6ae78720       message age 
> timer          3.08
>  designated port        800d                    forward delay 
> timer        0.00
>  designated cost          36                    hold 
> timer                 0.00
>  flags
> 
> 
> ro0ot wrote:
> 
> > I had this line for the br0 IP address: -
> >
> > ifconfig br0 192.168.1.1 netmask 255.255.255.0 broadcast 192.168.1.255
> >
> > Regards,
> > ro0ot
> >
> >
> > Bart De Schuymer wrote:
> >
> >> Op wo, 05-01-2005 te 01:39 +0800, schreef WL Siew:
> >>  
> >>
> >>> Hi,
> >>>
> >>> I had successfully setup my bridge (br0) but after few minutes the 
> >>> br0 interface seems not working.
> >>>
> >>> ifconfig eth0 0.0.0.0
> >>> ifconfig eth5 0.0.0.0
> >>>
> >>> brctl addbr br0
> >>>
> >>> brctl addif br0 eth0
> >>> brctl addif br0 eth5
> >>>
> >>> brctl stp br0 on
> >>>   
> >>
> >>
> >>> From the information you give, it seems that you assigned the IP 
> >>> address
> >>
> >> 0.0.0.0 to your bridge ports and you didn't to start the bridge itself.
> >> Your box therefore has no IP address and will therefore not respond to
> >> icmp messages.
> >>
> >> Try
> >> # ifconfig br0 $IP_ADDRESS
> >> A ping to $IP_ADDRESS from another host should then work (after you
> >> start the bridge it can take a few seconds before the bridge responds).
> >>
> >>  
> >>
> >>> I check on my system's /var/log/syslog file.  It shows something 
> >>> strange messages as below: -
> >>>
> >>> Jan  2 10:44:22 fw01 kernel: ipt_tcpmss_target: bad length (64 bytes)
> >>> Jan  2 10:44:32 fw01 last message repeated 11 times
> >>> Jan  2 12:27:08 fw01 kernel: Neighbour table overflow.
> >>> Jan  2 12:27:11 fw01 last message repeated 9 times
> >>> Jan  2 12:27:13 fw01 kernel: NET: 10 messages suppressed.
> >>>   
> >>
> >>
> >> Perhaps these are triggered by the fact that your network devices enter
> >> promiscuous mode.
> >>
> >>  
> >>
> >>> I unplug the network cable connected to the eth5 and run a ping to 
> >>> my router...the network is up again...I am able to ping my router.
> >>>   
> >>
> >>
> >> I'm assuming you are talking about the bridge box when you are talking
> >> about the router? The bridge ports of a bridge are by default not
> >> separately pingable. Only the IP address of the bridge (br0) device
> >> itself is pingable.
> >> You can change that behaviour by making a brouter. You can then assign
> >> IP addresses to the bridge ports and use them.
> >>
> >> cheers,
> >> Bart
> >>
> >>
> >>
> >>  
> >>
> >
> >
> >
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> >
> 
> 
> 
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