Bug 474645 - network scripts don't set interface MTU when bridging is enabled
Summary: network scripts don't set interface MTU when bridging is enabled
Keywords:
Status: CLOSED DUPLICATE of bug 463014
Alias: None
Product: Red Hat Enterprise Linux 5
Classification: Red Hat
Component: initscripts
Version: 5.4
Hardware: All
OS: Linux
low
medium
Target Milestone: rc
: ---
Assignee: initscripts Maintenance Team
QA Contact: BaseOS QE
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2008-12-04 18:50 UTC by Eduardo Habkost
Modified: 2008-12-04 18:58 UTC (History)
2 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed: 2008-12-04 18:58:07 UTC
Target Upstream Version:
Embargoed:


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Description Eduardo Habkost 2008-12-04 18:50:14 UTC
Description of problem:
When an interface is configured to be attached to a bridge, the MTU= line on ifcfg-ethX is ignored by the network setup scripts.


Version-Release number of selected component (if applicable):
initscripts-8.45.19.1.EL-1

How reproducible:
Always.


Steps to Reproduce:
# cat ifcfg-eth0
# Broadcom Corporation NetXtreme BCM5752 Gigabit Ethernet PCI Express
DEVICE=eth0
BOOTPROTO=none
HWADDR=00:19:B9:45:C2:CA
ONBOOT=yes
BRIDGE=br0
MTU=9000
# cat ifcfg-br0
TYPE=Bridge
DEVICE=br0
BOOTPROTO=dhcp
ONBOOT=yes
# ifup eth0
# ifup br0
Determining IP information for br0... done.
# ip link show eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:19:b9:45:c2:ca brd ff:ff:ff:ff:ff:ff


Actual results:
eth0 MTU kept as 1500.


Expected results:
eth0 MTU to be set as specified on ifcfg-eth0.

Additional info:
Bridging configuration is common on virtualization setups, and increasing the  MTU on network interfaces that support that is a recommended way of improving network performance. Being able to configure the MTU of interfaces attached to bridges is important on those cases.

Two patches from the upstream Fedora initscripts fix this issue (but they involve bonding also, so a simpler fix is possible for mtu/bridging setup only).
http://git.fedorahosted.org/git/?p=initscripts.git;a=commitdiff;h=15850b0
http://git.fedorahosted.org/git/?p=initscripts.git;a=commitdiff;h=f9cfaa36

Comment 1 Bill Nottingham 2008-12-04 18:58:07 UTC

*** This bug has been marked as a duplicate of bug 463014 ***


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