Brocade TurboIron 24X Series Configuration Guide - Manual (Page 661)

Brocade TurboIron 24X Series Configuration Guide 627
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Configuring OSPF
MD5 Authentication Wait Time: This parameter determines when a newly configured MD5
authentication key is valid. This parameter provides a graceful transition from one MD5 key to
another without disturbing the network. All new packets transmitted after the key activation wait
time interval use the newly configured MD5 Key. OSPF packets that contain the old MD5 key are
accepted for up to five minutes after the new MD5 key is in operation.
The range for the key activation wait time is from 0 – 14400 seconds. The default value is 300
seconds.
Hello Interval: The length of time between the transmission of hello packets. The range is 1 –
65535 seconds. The default is 10 seconds.
Retransmit Interval: The interval between the re-transmission of link state advertisements to
router adjacencies for this interface. The range is 0 – 3600 seconds. The default is 5 seconds.
Transmit Delay: The period of time it takes to transmit Link State Update packets on the interface.
The range is 0 – 3600 seconds. The default is 1 second.
Dead Interval: The number of seconds that a neighbor router waits for a hello packet from the
current router before declaring the router down. The range is 1 – 65535 seconds. The default is
40 seconds.
Changing the reference bandwidth for the cost on
OSPF interfaces
Each interface on which OSPF is enabled has a cost associated with it. The Layer 3 Switch
advertises its interfaces and their costs to OSPF neighbors. For example, if an interface has an
OSPF cost of ten, the Layer 3 Switch advertises the interface with a cost of ten to other OSPF
routers.
By default, an interface OSPF cost is based on the port speed of the interface. The cost is
calculated by dividing the reference bandwidth by the port speed. The default reference bandwidth
is 100 Mbps, which results in the following default costs:
• 10 Mbps port – 10
• All other port speeds – 1
You can change the reference bandwidth, to change the costs calculated by the software.
The software uses the following formula to calculate the cost.
Cost = reference-bandwidth/interface-speed
If the resulting cost is less than 1, the software rounds the cost up to 1. The default reference
bandwidth results in the following costs:
• 10 Mbps port cost = 100/10 = 10
• 100 Mbps port cost = 100/100 = 1
• 1000 Mbps port cost = 100/1000 = 0.10, which is rounded up to 1
• 155 Mbps port cost = 100/155 = 0.65, which is rounded up to 1
• 622 Mbps port cost = 100/622 = 0.16, which is rounded up to 1
• 2488 Mbps port cost = 100/2488 = 0.04, which is rounded up to 1
For 10 Gbps OSPF interfaces, in order to differentiate the costs between 100 Mbps, 1000 Mbps,
and 10,000 Mbps interfaces, you can set the auto-cost reference bandwidth to 10000, whereby
each slower link is given a higher cost, as follows: