5
BGP protocol. EGP supported by ES4624-SFP/ES4626-SFP switch include BGP-4, BGP-4+.
1.1.1 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 packets 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 packet 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
packet.
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 packets.
IP address of the next layer3 switch (next hop): specify the next layer3 switch the IP packet
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 packet forwarding according to the priority
order.
To prevent too large route table, a default route can be set. Once route table look up fails,
the default route will be chosen for forwarding packets.
The table below describes the routing protocols supported by ES4624-SFP/ES4626-SFP
switch and the default route look up priority value.
Routing Protocols or route type
Default priority value
Direct route
0
OSPF
110
Static route
1
RIP
120
OSPF ASE
150