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Cisco Bug: CSCun31285 - Nightster: Hi priority traffic is redirected to low priority channel

Last Modified

Dec 11, 2015

Products (1)

  • Cisco ASR 1000 Series Aggregation Services Routers

Known Affected Releases

15.4(2)S

Description (partial)

Symptom:
a. Problem is specific to ASR1001-X Built in Bay (bay 0)
b. The issue is when default ipv4 precedence based plim classification is used.
    TOS is 8 bits and its relation to ipv4 precedence is shown below.

+      * IP precedence, TOS, DSCP mapping.
+      * --------------------------------------------------------
+      * |  7  |   6  |   5  |   4  |   3  |   2  |   1  |   0  |
+      * --------------------------------------------------------
+      * <---- Precednce ---->
+      * <-------------- DSCP -------------------->
+      * <----------------------- TOS -------------------------->
+      * ---------------------------------------------------------------
+      * | TOS (8 bit)    |  Prec (3 bit)          |  DSCP (6 bit)     |
+      * ---------------------------------------------------------------
+      * | 0 - 255        | MSB 3 bits of TOS      | MSB 6 bits of TOS |
+      * |                | Prec 0 - TOS 0 - 31    | DSCP = n          |
+      * |                | Prec 1 - TOS 32 - 63   | TOS = { n*4,      |
+      * |                | Prec 2 - TOS 64 - 95   |         n*4 + 1,  |
+      * |                | Prec 3 - TOS 96 - 127  |         n*4 + 2,  |
+      * |                | Prec 4 - TOS 128 - 159 |         n*4 + 3 } |
+      * |                | Prec 5 - TOS 160 - 191 |                   |
+      * |                | Prec 6 - TOS 192 - 223 |                   |
+      * |                | Prec 7 - TOS 224 - 255 |                   |
+      * |--------------------------------------------------------------

 This issue is seen for ipv4 traffic with a TOS value such that lower significant 5 bits of TOS field are non-zero.
e.g 255 - binary 111 11111

Conditions:
This issue is seen for ipv4 traffic with a TOS value such that lower significant 5 bits of TOS field are non-zero.
e.g 255 - binary 111 11111
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