Bug 463340 - NM routed traffic over the slower of two interfaces.
NM routed traffic over the slower of two interfaces.
Product: Fedora
Classification: Fedora
Component: NetworkManager (Show other bugs)
All Linux
medium Severity medium
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Assigned To: Dan Williams
Fedora Extras Quality Assurance
Depends On:
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Reported: 2008-09-22 18:50 EDT by Dave Jones
Modified: 2015-01-04 17:30 EST (History)
4 users (show)

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Doc Type: Bug Fix
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Last Closed: 2009-02-14 15:12:01 EST
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Description Dave Jones 2008-09-22 18:50:59 EDT
I had my laptop plugged into my router via gigabit ethernet, and started scp'ing ~10GB of data to another machine.  At some point, NM realised it could auth with my access point, and get to the same host via wireless..

$ route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface     *          U     0      0        0 wlan0     *          U     0      0        0 eth0
default         firewall.kernel         UG    0      0        0 eth0

At this point, the scp slowed to a crawl (measured in KB/s rather than MB/s)

When I did an ifdown wlan0, the speed went back up again.

If we have a routable interface via ethernet, why bother bringing up wireless unless we ask for it?  (especially if they both end up with the same netmask)
Comment 1 Nick Boldt 2008-11-07 14:35:53 EST

See also https://bugzilla.redhat.com/show_bug.cgi?id=454955 for similar request / rationale.
Comment 2 Dan Williams 2009-02-14 15:12:01 EST
This should be fixed, NM will now use metrics with device routes so that faster devices (Ethernet > Wifi > Mobile Broadband) will have a lower metric, and thus be more preferred.

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