CoS QoS
Coolhandluke
Member Posts: 118
in CCNP
Hi,
Im sure quite a few people on the QoS exams can help but there must be some CCNP folk that can answer this too. When a frame is marked with a CoS value and then transferred across a trunk link, everything that I read implies that the 802.1Q info is stripped from the frame on receipt, this must include the CoS marking. I realise QoS settings could dictate how QoS information is handled but in a plain no QoS environment simply passing frames from trunk to trunk between switches, would a frame marked by a phone as CoS 5 go from switch A->B->C->D and maintain that CoS 5 Marking ?
The target environment is not cisco but am curious as to the process.
I assume that it depends on the order that the switch strips the information from a frame, i.e remove the .1q info only for ports that are untagged.
Any information is appreciated !
Im sure quite a few people on the QoS exams can help but there must be some CCNP folk that can answer this too. When a frame is marked with a CoS value and then transferred across a trunk link, everything that I read implies that the 802.1Q info is stripped from the frame on receipt, this must include the CoS marking. I realise QoS settings could dictate how QoS information is handled but in a plain no QoS environment simply passing frames from trunk to trunk between switches, would a frame marked by a phone as CoS 5 go from switch A->B->C->D and maintain that CoS 5 Marking ?
The target environment is not cisco but am curious as to the process.
I assume that it depends on the order that the switch strips the information from a frame, i.e remove the .1q info only for ports that are untagged.
Any information is appreciated !
[CCENT]->[CCNA]->[CCNP-ROUTE]->COLOR=#0000ff]CCNP SWITCH[/COLOR->[CCNP-TSHOOT]
Comments
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drkat
Banned Posts: 703
As far as I know the cos value on a trunk link is not stripped but only on a port that is untagged. If your target vendor isn't cisco you may have to retag the values. Generally cos/qos will match each of the link so if we're sending cos 5 out a trunk and it's received on a trunk the cos 5 will stay but if it's an access port then it will be stripped and either tagged or untagged depending on the port configuration. -
unclerico
Member Posts: 237 ■■■■□□□□□□
It depends on the other vendors implementation. With cisco, if the trunks between the switches are trusted and you have the same mappings on all switches in the chain then the 802.1p values will be retained.Preparing for CCIE Written
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networker050184
Mod Posts: 11,962 Mod
DSCP/IPP to 802.1p mapping is what you are looking for.An expert is a man who has made all the mistakes which can be made.