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870
BigIron RX Series Configuration Guide
53-1002253-01
Configuring IS-IS (IPv4)
28
The Designated IS is elected based on the priority of each IS in the broadcast network. When an IS
becomes operational, it sends a Level-1 or Level-2 Hello PDU to advertise itself to other ISs. If the
IS is configured to be both a Level-1 and a Level-2 IS, the IS sends a separate advertisement for
each level.
•
The Level-1 IS that has the highest priority becomes the Level-1 Designated IS for the
broadcast network.
•
The Level-2 IS that has the highest priority becomes the Level-2 Designated IS for the
broadcast network.
If the Designated IS becomes unavailable (for example, is rebooted), the IS with the next highest
priority becomes the new IS. If two or more ISs have the highest priority, the IS with the highest MAC
address becomes the Designated IS.
The priority is an interface parameter. Each interface that is enabled for IS-IS can have a different
priority.
Figure 118
shows an example of the results of Designated IS elections. For simplicity, this example
shows four of the five routers in
Figure 117
on page 868, with the same domain and areas.
FIGURE 118
Each broadcast network has a Level-1 designated IS and a Level-2 designated IS
Designated IS election has the following results in this network topology:
•
Router B is the Level-1 Designated IS for broadcast network 1
•
Router C is the Level-1 Designated IS for broadcast network 2
•
Router D is the Level-2 Designated IS for broadcast network 3
In this example, the IS-IS priorities for the IS-IS interfaces in broadcast network 1 have been
changed by an administrator. The priorities for the interfaces in the other broadcast networks are
still set to the default (64). When there is a tie, IS-IS selects the interface with the highest MAC
address.
Broadcast pseudonode
In a broadcast network, the Designated IS maintains and distributes link state information to other
ISs by maintaining a
pseudonode
. A pseudonode is a logical host representing all the Level-1 or
Level-2 links among the ISs in a broadcast network. Level-1 and Level-2 have separate
pseudonodes, although the same device can be the pseudonode for Level-1 and Level-2.
Router A
Router B
Router C
Router D
10
20
64
aaaa.bbbb.1111
64
aaaa.bbbb.1122
64
aaaa.bbbb.1121
64
aaaa.bbbb.1131
Broadcast
Network 1
Broadcast
Network 2
Broadcast
Network 3
Содержание BigIron RX Series
Страница 100: ...24 BigIron RX Series Configuration Guide 53 1002253 01 Logging on through the Web Management Interface 2 ...
Страница 192: ...116 BigIron RX Series Configuration Guide 53 1002253 01 Configuring authentication method lists 4 ...
Страница 228: ...152 BigIron RX Series Configuration Guide 53 1002253 01 Enabling WAN PHY mode support 6 ...
Страница 312: ...236 BigIron RX Series Configuration Guide 53 1002253 01 Displaying IP information 7 ...
Страница 356: ...280 BigIron RX Series Configuration Guide 53 1002253 01 Resetting LLDP statistics 9 ...
Страница 402: ...326 BigIron RX Series Configuration Guide 53 1002253 01 Transparent firewall mode 11 ...
Страница 432: ...356 BigIron RX Series Configuration Guide 53 1002253 01 SuperSpan 12 ...
Страница 500: ...424 BigIron RX Series Configuration Guide 53 1002253 01 MRP CLI example 14 ...
Страница 580: ...504 BigIron RX Series Configuration Guide 53 1002253 01 Configuring multicast traffic engineering 18 ...
Страница 591: ...BigIron RX Series Configuration Guide 515 53 1002253 01 Displaying traffic reduction 19 ...
Страница 592: ...516 BigIron RX Series Configuration Guide 53 1002253 01 Displaying traffic reduction 19 ...
Страница 598: ...522 BigIron RX Series Configuration Guide 53 1002253 01 Viewing Layer 2 ACLs 20 ...
Страница 656: ...580 BigIron RX Series Configuration Guide 53 1002253 01 Trunk formation 22 ...
Страница 754: ...678 BigIron RX Series Configuration Guide 53 1002253 01 Displaying RIP filters 24 ...
Страница 814: ...738 BigIron RX Series Configuration Guide 53 1002253 01 Displaying OSPF information 25 ...
Страница 932: ...856 BigIron RX Series Configuration Guide 53 1002253 01 Generalized TTL security mechanism support 26 ...
Страница 980: ...904 BigIron RX Series Configuration Guide 53 1002253 01 Clearing IS IS information 28 ...
Страница 1000: ...924 BigIron RX Series Configuration Guide 53 1002253 01 Using secure copy 30 ...
Страница 1088: ...1012 BigIron RX Series Configuration Guide 53 1002253 01 IP source guard 35 ...
Страница 1108: ...1032 BigIron RX Series Configuration Guide 53 1002253 01 Reading CDP packets 37 ...
Страница 1126: ...1050 BigIron RX Series Configuration Guide 53 1002253 01 Clearing sFlow statistics 39 ...
Страница 1140: ...1064 BigIron RX Series Configuration Guide 53 1002253 01 802 1s Multiple Spanning Tree Protocol 40 ...
Страница 1324: ...1248 BigIron RX Series Configuration Guide 53 1002253 01 Displaying OSPFv3 information 48 ...
Страница 1363: ...BigIron RX Series Configuration Guide 1287 53 1002253 01 Continuous System Monitor 51 ...
Страница 1364: ...1288 BigIron RX Series Configuration Guide 53 1002253 01 Continuous System Monitor 51 ...
Страница 1404: ...1328 BigIron RX Series Configuration Guide 53 1002253 01 Commands That Require a Reload D ...
Страница 1458: ...1382 BigIron RX Series Configuration Guide 53 1002253 01 VSRP E ...