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253
Administration for Network Connectivity
555-233-504 — Issue 1 — April 2000 CID: 77730
A Screens Reference
Metric The metric value indicates the desirability of the IP route in terms of the efficiency of
the data transmission between two nodes.
If there are two routes to the same destination, one with metric 0 and one with metric
1, the switch software will choose the route with metric 0 because it is (if properly
administered) the more efficient route of the two. On the other hand, if both routes are
administered with metric 0, the switch will choose whichever it sees first, not
necessarily the most efficient one.
By entering 1 in the Metric field, you are telling the switch, “this is a complex route;
if you know of a simpler route (metric 0) to this destination, use that instead.” In other
words, metric 1 diverts usage of the route to a metric-0 route, if available.
The following diagram illustrates the use of the Metric field. Switches A and C are
connected via switch B over two LANs. Switch B has two C-LAN boards, which are
connected via a ppp link. The network nodes are numbered 1 through 6.
The following IP routes are required for communications between switches A and C:
Administered Destination Gateway
Route
on Board Loc.Node Node Metric
1 Switch A C-LANa 6 2 0
2 Switch B C-LAN1 6 4 1
3 Switch B C-LAN2 1 3 1
4 Switch C C-LANc 1 5 0
Implied Switch B C-LAN2 6 5 0
The implied route from C-LAN2 to node 6 via node 5 is not administered on the IP
Routing screen but is a built-in part of the C-LAN firmware and the automatic subnet
routing feature. (We are assuming that automatic subnet routing is enabled for node 5
on the Data Module screen.) Therefore, on Switch B there are two routes to
destination 6 — route 2 and the implied route.
Valid Values Usage
0 or 1 A metric value of 1 is used only on a switch that has more than
one C-LAN board installed.
You can always enter either 0 or 1 in the Metric field but the
choice should be guided by the information below.
LAN
LAN
C-LAN2
C-LAN1
C-LANa
2
1
3
4
5
Switch A
Switch B
Switch C
6
ppp
ethernet
ethernet
C-LANc