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OSPF * and traffic share count

Posted on 2010-08-18
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Last Modified: 2012-06-27
What does the * and the traffic share count mean?

Will the traffic be equal cost load balanced between the two paths xxx.xx.192.3 and xxx.xx..192.4?



switch#sh ip route 11.136.10.26
Routing entry for 11.136.0.0/16
  Known via "ospf 777", distance 110, metric 2, type intra area
  Last update from xxx.xx.192.4 on Vlan900, 01:12:38 ago
  Routing Descriptor Blocks:
  * xxx.xx..192.4, from xxx.xx..136.4, 01:12:38 ago, via Vlan900
      Route metric is 2, traffic share count is 1
    xxx.xx..192.3, from xxx.xx..136.4, 01:12:38 ago, via Vlan900
      Route metric is 2, traffic share count is 1

switch#sh ip route xxx.xx..192.4
Routing entry for xxx.xx..192.0/24
  Known via "connected", distance 0, metric 0 (connected, via interface)
  Routing Descriptor Blocks:
  * directly connected, via Vlan900
      Route metric is 0, traffic share count is 1
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Question by:Dragon0x40
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by:rfc1180
Comment Utility
The 2 routes you see are the equal cost routes (I am sure you know this); each block is one route, the asterisk "*" next to one of the block entries (The first one is this case) corresponds to the active route that will be used for any new traffic (This could be for a single packet or an entire new flow to the destination).

Billy
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Author Comment

by:Dragon0x40
Comment Utility
thanks rfc1180,

when I run the show ip route 11.136.0.0 and repeat many times the * never moves to the other route?

According to the following  link "traffic share count 1" means that 1 packet goes on one route and the next 1 packet goes the next route and alternates packet by packet. Does not make sense to me as what you said about flows being switched makes more sense.

http://www.mail-archive.com/cisco@groupstudy.com/msg102296.html
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by:rfc1180
Comment Utility
it depending what you are using for the switching method:

CEF:
Per-Destination and Per-Packet Load Balancing

Billy
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Author Comment

by:Dragon0x40
Comment Utility
How do I tell which switching method I am using?

Does the traffic show that I am not routing any packets through CEF?

#sh ip cef detail
IP Distributed CEF with switching (Table Version 1367), flags=0x0
  547 routes, 0 reresolve, 0 unresolved (0 old, 0 new), peak 1
  9 instant recursive resolutions, 0 used background process
  547 leaves, 48 nodes, 126800 bytes, 973 inserts, 426 invalidations
  5 load sharing elements, 1680 bytes, 5 references
  universal per-destination load sharing algorithm, id 17093EB8
  3(0) CEF resets, 229 revisions of existing leaves
  Resolution Timer: Exponential (currently 1s, peak 1s)
  224 in-place/0 aborted modifications
  refcounts:  13594 leaf, 12544 node

  Table epoch: 0 (547 entries at this epoch)

Adjacency Table has 516 adjacencies
0.0.0.0/0, version 966, epoch 0, cached adjacency 10.192.9.1
0 packets, 0 bytes
  via 10.192.9.1, 0 dependencies, recursive
    next hop 10.192.9.1, GigabitEthernet9/48 via 10.192.9.1/32 (Default)
    valid cached adjacency
0.0.0.0/32, version 0, epoch 0, receive

11.136.0.0/16, version 1356, epoch 0
0 packets, 0 bytes
  via xxx.xx..192.4, Vlan900, 0 dependencies
    traffic share 1
    next hop xxx.xx..192.4, Vlan900
    valid adjacency
  via xxx.xx..192.3, Vlan900, 0 dependencies
    traffic share 1
    next hop xxx.xx..192.3, Vlan900
    valid adjacency
  0 packets, 0 bytes switched through the prefix
  tmstats: external 0 packets, 0 bytes
           internal 0 packets, 0 bytes

#sh ip cef traffic prefix-length
IP prefix length switching statistics:
----------------------------------------
Prefix       Number of       Number of
Length       Packets         Bytes
----------------------------------------
     0               0               0
     1               0               0
     2               0               0
     3               0               0
     4               0               0
     5               0               0
     6               0               0
     7               0               0
     8               0               0
     9               0               0
    10               0               0
    11               0               0
    12               0               0
    13               0               0
    14               0               0
    15               0               0
    16               0               0
    17               0               0
    18               0               0
    19               0               0
    20               0               0
    21               0               0
    22               0               0
    23               0               0
    24               0               0
    25               0               0
    26               0               0
    27               0               0
    28               0               0
----------------------------------------
Prefix       Number of       Number of
Length       Packets         Bytes
----------------------------------------
    29               0               0
    30               0               0
    31               0               0
    32               0               0
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rfc1180 earned 500 total points
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 5 load sharing elements, 1680 bytes, 5 references
  universal per-destination load sharing algorithm, id 17093EB8

Billy
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