3Com 4007R Implementation Guide - Page 551

AppleTalk Routes 551 Important Considerations Before administering AppleTalk routes, review the following guidelines and considerations: s The RTMP table supports a maximum of 514 entries. s AppleTalk supports a maximum distance of 15 hops. s A hop count of 0 represents a network that is directly connected to the router. s When an AppleTalk router starts up on the network, the first entries in its routing table are the network numbers to which it is directly attached. s Node numbers are dynamically assigned and often change when the router restarts. s Each 16 bit number within a network range is capable of supporting 253 network nodes. s When a router receives an RTMP packet that contains a routing entry currently not in its table, the router adds the entry to its routing table, and increments the route's distance (hop count) by 1. s When a network is removed from the RTMP table (whether manually or though the aging process), the router also scans the Zone Information Table (ZIT), and removes ZIT entries that contain the deleted network number. s If the Zone Information Table contains an entry whose network number range is not in the RTMP table, the router then concludes that the network is no longer on the Internet and deletes the network's ZIT entry. s An overburdened network with many routers can prevent some routers from sending RTMP updates every 10 seconds. Because routers begin to age out routes after the loss of 2 successive RTMP updates, the failure for RTMP packets to arrive may result in unnecessary route changes, known as route flapping. For this reason, keep network segments to a reasonable size.