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Old 04-17-2013, 02:41 PM   #1
irreverentryan
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Bridged adapters causing broadcast storm


I have four ethernet adapters, split into two bridged adapters; br0 and br1. br0 consists of em1 and em2, br1 consists of em3 and em4. if I leave em2 and em4 unplugged, I can create both bridges, however once they are created and I plug in the remaining adapters for the bridge, they cause a network storm. The following are my configuration files for each interface and bridge:

///////br0/////////
DEVICE=br0
BOOTPROTO=static
ONBOOT=yes
TYPE=Bridge
IPV6INIT=no
USERCTL=no
GATEWAY=192.168.1.244
NETMASK=255.255.252.0
IPADDR=192.168.1.16
DNS1=192.168.1.39
DNS2=192.168.1.150

////////em1/////////
DEVICE="em1"
BOOTPROTO=none
NM_CONTROLLED=no
ONBOOT=yes
TYPE="Ethernet"
UUID="463c42ca-6d94-42a0-84af-76933e508554"
HWADDR=00:21:9B:A7:40:4C
BRIDGE=br0
PEERDNS=yes
PEERROUTES=yes
LAST_CONNECT=1366218148

///////em2/////////
DEVICE="em2"
BOOTPROTO=none
NM_CONTROLLED=no
ONBOOT=yes
TYPE="Ethernet"
HWADDR=00:21:9B:A7:40:4E
BRIDGE=br0
PEERDNS=yes
PEERROUTES=yes
LAST_CONNECT=1366218148

////////br1////////
DEVICE=br1
BOOTPROTO=static
ONBOOT=yes
TYPE=Bridge
IPV6INIT=no
USERCTL=no
NETMASK=255.255.255.0
IPADDR=192.168.10.100
DNS1=192.168.1.39
DNS2=192.168.1.150

////////em3///////
DEVICE="em3"
BOOTPROTO=none
NM_CONTROLLED=no
ONBOOT=yes
TYPE="Ethernet"
HWADDR=00:21:9B:A7:40:50
BRIDGE=br1

////////em4////////
DEVICE="em4"
BOOTPROTO=none
NM_CONTROLLED=no
ONBOOT=yes
TYPE="Ethernet"
HWADDR=00:21:9B:A7:40:52
BRIDGE=br1

Parts of the bridge seem to be working; for instance, I can use either em1 or em2 with a cable, and send and receive pings using the same address, but if both are plugged in (on either bridge) then I get a broadcast storm.
 
Old 04-17-2013, 06:21 PM   #2
David1357
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Quote:
Originally Posted by irreverentryan View Post
...however once they are created and I plug in the remaining adapters for the bridge, they cause a network storm
How are the adapters connected to the rest of your network?
Do you really want a netmask of "255.255.252.0" for br0?
Is your network connected to any other bridges? If so, you may need to enable spanning tree protocol (STP) on your bridges.
 
Old 04-17-2013, 06:33 PM   #3
warez74
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Registered: Apr 2013
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Hello,

Probably you have some layer 2 loops without knowing about it.

Can you provide some sort of schema or drawing on current network topology (how the eth devices are connected to outer world)?

e.g.:

em1>switch1(vlan1 port1)
etc
 
Old 04-18-2013, 12:34 PM   #4
irreverentryan
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em1->switch1->port C11->Vlan1
em2->switch1->port C14->Vlan1
em3->switch2->port 7->Vlan1
em4->switch2->port 8->Vlan1

switch 1 and switch 2 are completely separated. Their only connecting point would be this one server, via its bridges (which are not IPforwarding atm.) siwtch2 is my storage network, switch1 is our production network. The production network is a /22 so the 255.255.252.0 subnet is correct.

if I config both bridges, but only physically plug in em1 and em3, then the server acts fine. Pings both networks, goes online, etc. if I plug in em2 or em4, then I get a broadcast storm on the respective switch.
 
Old 04-18-2013, 02:00 PM   #5
warez74
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Ok, the things are much more clear now.

Well, as I expected, you have over there 2 loops at layer 2.

You cannot bridge em1 and em2 because that would act the same as if you connected port C11 to port C14 using a straight ethernet cable:
C11>cable>C14

Get it? Same rule goes for port 7 and port 8.

You can thought of bridge like it was a switch. Therefore, bridging two ports in the same broadcast domain will trigger the arp storm.

Here arises another question, why do you need two ethernet interfaces per bridge? Maybe you wanted to actually bond (interface bonding) to increase the throughput?

@David1357

Good point, STP should automatically detect loops and disable one of the eth interfaces in the bridge. Right?

Last edited by warez74; 04-18-2013 at 02:02 PM. Reason: adding something
 
Old 04-18-2013, 02:03 PM   #6
irreverentryan
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That sounds like my issue! I thought they were the same. I'll look into bonding, thank you!
 
Old 04-18-2013, 02:06 PM   #7
warez74
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You're welcome

Good luck,
Regards
 
  


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