Hello everyone!
Next, let's continue to learn about routing.
What is Static Route
A static route is a special route that is manually configured by a network administrator. Static routes are easy to configure and do not need to occupy CPU resources to calculate and analyze routes as dynamic routes do.
The disadvantage of static routes is that they cannot adapt to the change in a network automatically, so network changes require manual reconfiguration.
Static routes are fit for networks with comparatively simple structures. It is not advisable to configure and maintain static routes for a network with a complex structure. Static routes do however reduce the effect of bandwidth and CPU resource consumption that occurs when other protocols are implemented.
Configuring a Static Route
//On R1, configure a static route with the destination address 172.16.2.0/24 and next-hop 172.16.100.2.
[RT1]ip route-static 172.16.2.0 24 172.16.100.2
//Data packets from PC1 to PC2 can be forwarded to PC2. However, because the communication between two data nodes is bidirectional, the data packets from PC2 to PC1 are still discarded. Therefore, a static route with the destination address 172.16.1.0/24 and next-hop 172.16.100.1 must be configured on R2
[RT2]ip route-static 172.16.1.0 24 172.16.100.1
You can configure static routes in either of the following ways:
Method 1: Associate the next-hop IP address.
[Quidway]ip route-static 172.16.2.0 24 172.16.100.2
-172.16.2.0 is the destination network address of the route.
-24 is the network mask or mask length of the destination network. The value 24 is equivalent to 255.255.255.0.
-172.16.100.2 is the next-hop IP address to the network.
Method 2: Associating the outbound interface
[Quidway]ip route-static 172.16.2.0 24 GigabitEthernet0/0/1
-172.16.2.0 is the destination network address of the route
-24 is the network mask or mask length of the destination network. The value 24 is equivalent to 255.255.255.0.
-GigabitEthernet0/O/1 is the outbound interface to the network.
-If the outbound interface is a route is a point-to-point interface (for example, a serial interface encapsulated with HDLC or PPP), the route can be associated with only the outbound interface. If the outbound interface is a broadcast multi-access interface, for example, an Ethernet interface, the outbound interface must be associated with the next hop. Otherwise, the router cannot forward the packet to the correct next hop.
Static routes can be applied to serial networks or Ethernet networks, but their configurations are different.
ip route-static ip-address { mask | mask-length } interface-type interface-number[ next-hop-address ], this command is used to configure static routes. ip-address specifies the destination address of a network or host, and mask specifies the length of a subnet mask or prefix. The following parameters specify the next hop or outbound interface.
When configuring a static route on a serial network, you can specify only the next-hop address (for example, 10.0.12.1) or specify only interface-type and interface-number(for example, Serial 0/0/2) to configure an outbound interface. On Huawei ARG3 series routers, serial interfaces are encapsulated with PPP by default. For this type of interface, the next-hop address of the static route is the address of the peer interface connected to the interface. Therefore, you can configure only the outbound interface when configuring the static route on the serial network.
When configuring a static route on a broadcast interface, you must specify the next-hop address. On an Ethernet, a network may be connected to multiple routers. If only the outbound interface is specified when you configure a static route, the router cannot forward packets to the correct next hop.
Floating Static Route
A floating static route is a special static route. You can configure a static route with a greater administrative distance than the primary route to provide a backup route when the primary route fails. However, if the primary route exists, it does not appear in the routing table. Floating static routes are mainly used for dial-up backup.
As shown in the preceding figure, R3 and its downstream network are reachable to 10.9.9.0/24 through R1 and R2. The two routes are added to the R3 routing table. This phenomenon is called equal-cost load balancing.
The traffic forwarded by R3 to 10.9.9.0/24 uses R1 or R2 as the next hop. The disadvantage is that the packets to the destination may be in disorder. If traffic is forwarded only to R1 and is switched when R1 fails, you can configure a floating static route.
The two routes are destined for the same destination but use different next-hop IP addresses. In addition, the two routes have the same priority and cost (the cost is 0).
By, default, the preference of a static route is 60, and we change the preference of the other static route to 80. After preference comparison, the route with a smaller preference value is preferred and added to the routing table for data forwarding. The other static route with preference value 80 is hidden and does not exist in the routing table.
When R1 breaks down or the direct link between R3 and R1 fails, the other route emerges and traffic is switched to the link between R3 and R2. This is a good path backup mechanism.
Default Route
The default route is a special route whose destination address and mask are all 0.
If the routing table does not contain an entry that matches the destination address of a packet, the device selects the default route as the forwarding path of the packet.
As shown in the figure, if RTA needs to reach the network directly connected to RTB, a route is required. If static routes are used to add routes for RTA, three static routes are required for the three destination networks. This not only increases the configuration workload of RTA but also increases the burden of maintaining the routing table. Therefore, to ensure network reachability and reduce the number of routes, you can configure a default route as follows:
[RTA]ip route-static 0.0.0.0 0.0.0.0 10.0.12.2
[RTA]ip route-static 0.0.0.0 0.0.0.0 10.0.12.2
In this example, RTA uses the default route to forwarding packets destined for unknown destination addresses. The default preference of the default static route is 60. During route selection, the default route is finally matched.
VLAN Limitations
VLAN isolated two broadcast domains, and also strictly isolated layer 2 traffic between VLAN. Users belonging to different VLANs could not manage Layer 2 communication.
VLAN Routing – L3 Switch
Configure the VLANIF interface on the Layer 3 switch as the gateway to implement inter-VLAN routing. If there are multiple VLANs on the network, configure a VLANIF interface for each VLAN and assign an IP address to each VLANIF interface. The default gateway configured on the user PC is the IP address of the VLANIF interface on the Layer 3 switch. When checking the IP routing table of the switch, you can find that only the route to the directly connected network segment can be found. Therefore, you need to set up a route to the indirectly connected network segment. You can configure a static route.
After configuring the default route on SWA, the path to PC2/3 will be found by checking the routing table. So as SWB. Static routing is configured on both SWA and SWB, where default routing is used, and the next-hop address respectively points to Vlanif5:10.1.12.2 of SWB and Vlanif5:10.1.12.1 of SWA.
Thanks for reading!
