SNR S2989G-48TX-DC — настройка IPv6 Black Hole Routing для предотвращения зацикливания [534/553]

S2989G-24TX Operation Manual

Chapter 11 IPv6 Configuration

11-24

Figure 11-4 IPv6 Black Hole Routing Configuration Example

As it is shown in the figure, in Switch 2, eight in all interfaces are configured as Layer

3 VLAN interfaces for access interfaces. The network addresses are

2004:1:2:3:1/80~2004:1:2:3:7/80. A default routing is configured on Switch 2 to connect to

Switch 1. And a backward default routing is configured on Switch 1 to Switch 2, whose

network address is 2004:1:2:3::/64. Commonly, this configuration will work well. However,

if one of the Layer 3 interfaces in Switch 2 goes down, for example, the interface belonged

to 2004:1:2:3:1/80. When datagrams arrives at VLAN1 in Switch 2, there will be no routing

rules for these datagrams. The switch then will forward these datagrams according to the

default routing, back to Switch 1. When Switch 1 receives these datagrams, it will forward

them back to Switch 2. Thus, loopback exists. To solve this problem, Black Hole Routing

can be introduced on Switch 2.

ipv6 route 2004:1:2:3::/64 null0 50

Then Switch 2 will drop the datagrams from interface VLAN1 that match the Black

Hole Routing rule. And loopback routing is prevented.

Configuration steps are listed as below:

Switch#config

Switch(config)#ipv6 route 2004:1:2:3::/64 null0 50

11.4.4

Black Hole Routing Troubleshooting

When configuring the Black Hole Routing function, the configuration may not work

due to some reasons such as incorrect network address mask, and incorrect

management distance. Attention should be paid to the following items:

 IPv6 should be enabled before IPv6 Black Hole Routing can work.

 It is suggested that the length of the network address mask should be longer than that

of normal routing configuration, in order to prevent the Black Hole Routing from

2004:1:2:3::1/64

SWITCH1

SWITCH2

2004:1:2:3::2/64

2004:1:2:3:1::/80

………

2004:1:2:3:7::/80