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Lee_Sutcliffe_5's avatar
Lee_Sutcliffe_5
Icon for Nimbostratus rankNimbostratus
Jun 24, 2015

VS Precedence

Hi

I have a question relating to VS precedence and which VS would process the packet in the following example:

Packet  - destination IP  > 10.10.10.10 destination port > TCP/80

VIP-A 10.10.10.0:80
 protocol tcp
 mask 255.255.255.0

VIP-B 10.10.10.10:80
 protocol udp
 mask 255.255.255.255

My understanding having read https://support.f5.com/kb/en-us/solutions/public/6000/400/sol6459.html is that there is a higher emphasis on the VS with the longest subnet match.

However, in the in above example, this would be VIP-B - but the protocol for this VS is UDP.

Would VIP-B process the request and subsequently drop traffic - or is the BigIP intelligent enough to match on a VS with a lower precedence, but one that has the correct protocol configured?

Many thanks

Lee

application delivery
LTM
TMOS
vip
vs

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  • JRahm's avatar
    JRahm
    Icon for Admin rankAdmin
    Jun 24, 2015

    Hi Lee, When a listener lookup occurs, the precedence linked above matches as expected for all matching traffic types. For example, consider the following three virtuals:

     

    1. 10.10.10.0:0/25 *All Protocols
    2. 10.10.10.0:0/25 *UDP
    3. 10.10.10.0:0/24 *TCP

    If you send an http request to 10.10.10.40, the vip 1 will receive the traffic. If you send an http request to 10.10.10.140, vip 3 will receive the traffic. If you delete vip 1 and retry an http request to 10.10.10.40, it will bypass vip 2 because of a protocol mismatch and match vip 3.

     

    So to answer your question, yes, the precedence matters first, but only when the virtual is capable of handling that traffic. A UDP virtual, even with a longer match, isn't capable of handling TCP traffic, so it doesn't apply.

     

  • Lee_Sutcliffe's avatar
    Lee_Sutcliffe
    Icon for Nacreous rankNacreous
    Jun 25, 2015

    Hi Jason,

     

    Thanks for your explanation, that question has been bugging me for a while!

     

    Lee