Cabletron Systems DMS-100 User Manual

Page 60

60 Chapter 2: EIU messaging protocols

297-8991-910 Standard 03.01 August 1999

Routing tables

The IP routing table structure is briefly explained here. The knowledge of IP
routing tables is critical in understanding SuperNode IP routing issues.

The SuperNode IP routing information is organized locally on all hosts in two
separate tables. One table determines a routeset from a given destination IP
address. An example of this table is shown in table 3. A second table is used
to determine the actual next hop IP address from the routeset derived from the
first table. An example of this table is shown in table 4.

These two tables are not datafilled through table control, rather they are
derived from control datafill in tables IPNETWRK, IPROUTER, and
IPHOST. Further, these two tables may contain entries from dynamically
learned routes either from RIP on the EIU or from ICMP redirect messages on
other nodes.

Each routing-table entry (see table 3) contains a destination IP address, IP
address subnet mask, list of route lists (routeset) that reach the destination IP,
and other fields that indicate type of route and subnet type. The IP routing
algorithm is used to determine the routeset that can reach the destination IP
address.

Each route list table entry (see table 4) contains one route list. The route list is
composed of a list of routers that share common router characteristics. For
instance, all EIU IP routers configured on the same LAN are grouped in one
route list. The primary router is determined in each route list entry. For a given
host node, the primary router is the EIU that packets are sent to. The primary

Table 3

IP routing table

Destination

Subnet Mask

Routeset

Type of Route

Subnet

47.12.0.0

255.255.240.0

{1, 0, 0, 0, 0}

Gateway

SuperNode

47.148.0.0

255.255.240.0

{2, 0, 0, 0, 0}

Gateway

SuperNode

0.0.0.0

{2, 1, 0, 0, 0}

Default

SuperNode

Table 4

IP route list table

Index

Type of route list

Node

Status

Address

Router

EIU 132 * Primary

InSv

47.64.64.4

Router-Host

EIU 131

EIU 133

EIU 205 * Primary

OutSv

InSv

47.64.64.2

47.64.64.5

47.64.64.3