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protocol, so that multiple routing protocols can be associated.
EGP is used to exchange routing information among different autonomous systems,
such as BGP protocol. EGP supported by ES4700 series switch include BGP-4, BGP-4+.
14.1.1 Routing Table
As mentioned before, layer3 switch is mainly used to establish the route from the
current layer3 switch to a network or a host, and to forward packages according to the
route. Each layer3 switch has its own route table containing all routes used by that switch.
Each route entry in the route table specifies the physical port should be used for
forwarding package to reach a destination host or the next hop layer3 switch to the host.
The route table mainly consists of the following:
Destination address: used to identify the destination address or destination network
of an IP package.
Network mask: used together with destination address to identify the destination host
or the network the layer3 switch resides. Network mask consists of several consecutive
binary 1's, and usually in the format of dotted decimal (an address consists of 1 to 4
255’s.) When “AND” the destination address with network mask, we can get the network
address for the destination host or the network the layer3 switch resides. For example,
the network address of a host or the segment the layer3 switch resides with a destination
address of 200.1.1.1 and mask 255.255.255.0 is 200.1.1.0..
Output interface: specify the interface of layer3 switch to forward IP packages.
IP address of the next layer3 switch (next hop): specify the next layer3 switch the IP
package will pass.
Route entry priority: There may be several different next hop routes leading to the
same destination. Those routes may be discovered by different dynamic routing protocols
or static routes manually configured. The entry with the highest priority (smallest value)
becomes the current best route. The user can configure several routes of different priority
to the same destination; layer3 switch will choose one route for IP package forwarding
according to the priority order.
To avoid too large route table, a default route can be set. Once route table lookup
fails, the default route will be chosen for forwarding packages.
The table below describes the routing protocols supported by ES4700 series and the
default route lookup priority value.
Routing Protocols or route type
Default priority value
Direct route
0
OSPF 110
Static route
1
RIP 120
