08-05-2009 10:32 PM - edited 03-06-2019 07:06 AM
Hi,
what will happen when a device gets a runt and giant packet.
regards
Neo
08-05-2009 11:36 PM
Hi Neo
They will be discarded.
Giants:
Description: CatOS sh port and Cisco IOS sh interfaces and sh interfaces counters errors. Frames received that exceed the maximum IEEE 802.3 frame size (1518 bytes for non-jumbo Ethernet) and have a bad Frame Check Sequence (FCS).
Common Causes: In many cases, this is the
result of a bad NIC. Try to find the offending device and remove it from the network.
Platform Exceptions: Catalyst Cat4000
Series that run Cisco IOS Previous to
software Version 12.1(19)EW, the giants
counter incremented for a frame > 1518bytes.
After 12.1(19)EW, a giant in show interfaces increments only when a frame is received >1518bytes with a bad FCS.
Runts:
Description: CatOS sh port and Cisco IOS sh interfaces and sh interfaces counters errors.
The frames received that are smaller than the minimum IEEE 802.3 frame size (64 bytes for Ethernet), and with a bad CRC.
Common Causes: This can be caused by a
duplex mismatch and physical problems, such as a bad cable, port, or NIC on the attached device.
Platform Exceptions: Catalyst 4000 Series
that run Cisco IOS Previous to software
Version 12.1(19)EW, a runt = undersize.
Undersize = frame < 64bytes. The runt counter only incremented when a frame less than 64 bytes was received. After 12.1(19EW, a runt = a fragment. A fragment is a frame < 64 bytes but with a bad CRC. The result is the runt counter now increments in show interfaces, along with the fragments counter in show interfaces counters errors when a frame <64 bytes with a bad CRC is received.
/Mikael
08-06-2009 11:15 AM
Just wanted to add something..
Most switches could report 801.1q tagged frames as giants and they won't get dropped. This happens if a frames that is coming to the switch is 1518 bytes long + 4 bytes of dot1q = 1522
The switch will strip the tag, report the giant but will still let the frame get in without getting dropped.
If you see a giant, what you do is check the:
Core3560#sh controllers ethernet-controller f0/1
Look for:
- Invalid frames, too large
- Valid frames, too large
Example:
sh int fa 0/1 sees 288 giants but sh controller eth f0/1 sees 288 Valid frames, too large ===== no problem
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide