Help Center/ Virtual Private Cloud/ User Guide/ Elastic Network Interface and Supplementary Network Interface/ Network Interface Configuration Examples/ Configuring Policy-based Routes for an ECS with Multiple Network Interfaces/ Configuring IPv4 and IPv6 Policy-based Routes for a Linux ECS with Multiple Network Interfaces (CentOS)

Updated on 2024-12-02 GMT+08:00

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Configuring IPv4 and IPv6 Policy-based Routes for a Linux ECS with Multiple Network Interfaces (CentOS)

Scenarios

This section describes how to configure policy-based routes for a CentOS 8.0 64-bit ECS with two network interfaces.

IPv4: Configuring IPv4 Policy-based Routes for a CentOS ECS
IPv6: Configuring IPv6 Policy-based Routes for a CentOS ECS

For details about the background knowledge and networking of an ECS with two network interfaces, see Overview.

Configuring IPv4 Policy-based Routes for a CentOS ECS

Collect the ECS network information required for configuring policy-based routes.

For details, see Collecting ECS Network Information.

In this example, the network information of the ECS is shown in Table 1.

**Table 1** CentOS ECS using IPv4
ECS	Primary Network Interface	Extended Network Interface
Source	IP address: 10.0.0.115 Subnet: 10.0.0.0/24 Subnet gateway: 10.0.0.1	IP address: 10.0.1.183 Subnet: 10.0.1.0/24 Subnet gateway: 10.0.1.1
Destination	IP address: 10.0.2.12	N/A

Log in to the source ECS.
For details, see How Do I Log In to My ECS?
Check whether the source ECS can use its primary network interface to communicate with the destination ECS:
ping -I <IP-address-of-the-primary-network-interface-on-the-source-ECS> <IP-address-of-the-destination-ECS>

In this example, run the following command:

ping -I 10.0.0.115 10.0.2.12
If information similar to the following is displayed, the source ECS can use its primary network interface to communicate with the destination ECS.
```
[root@ecs-resource ~]# ping -I 10.0.0.115 10.0.2.12
PING 10.0.2.12 (10.0.2.12) from 10.0.0.115 : 56(84) bytes of data.
64 bytes from 10.0.2.12: icmp_seq=1 ttl=64 time=0.775 ms
64 bytes from 10.0.2.12: icmp_seq=2 ttl=64 time=0.268 ms
64 bytes from 10.0.2.12: icmp_seq=3 ttl=64 time=0.220 ms
64 bytes from 10.0.2.12: icmp_seq=4 ttl=64 time=0.167 ms
^C
--- 10.0.2.12 ping statistics ---
```
Before configuring policy-based routes, ensure that the source ECS can use its primary network interface to communicate with the destination ECS.

Query the network interface names of the source ECS:

ifconfig

Search for the network interface names based on IP addresses.

The primary network interface address is 10.0.0.115, and its name is eth0.
The extended network interface address is 10.0.1.183, and its name is eth1.

[root@ecs-resource ~]# ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 10.0.0.115  netmask 255.255.255.0  broadcast 10.0.0.255
        inet6 fe80::f816:3eff:fe92:6e0e  prefixlen 64  scopeid 0x20<link>
        ether fa:16:3e:92:6e:0e  txqueuelen 1000  (Ethernet)
        RX packets 432288  bytes 135762012 (129.4 MiB)
        RX errors 0  dropped 0  overruns 0  frame 1655
        TX packets 423744  bytes 106716932 (101.7 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

eth1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 10.0.1.183  netmask 255.255.255.0  broadcast 10.0.1.255
        inet6 fe80::f816:3eff:febf:5818  prefixlen 64  scopeid 0x20<link>
        ether fa:16:3e:bf:58:18  txqueuelen 1000  (Ethernet)
        RX packets 9028  bytes 536972 (524.3 KiB)
        RX errors 0  dropped 0  overruns 0  frame 1915
        TX packets 6290  bytes 272473 (266.0 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

Configure temporary routes for the source ECS.

Temporary routes are applied immediately but are lost after ECS restarts. To avoid network disruptions, perform 6 to configure persistent routes instead.
1. Configure policy-based routes for both the primary and extended network interfaces.
  - Primary network interface
    ip route add default via <subnet-gateway> dev <network-interface-name> table <route-table-name>
    
    ip route add <subnet-CIDR-block> dev <network-interface-name> table <route-table-name>
    
    ip rule add from <network-interface-address> table <route-table-name>
  - Extended network interface
    ip route add default via <subnet-gateway> dev <network-interface-name> table <route-table-name>
    
    ip route add <subnet-CIDR-block> dev <network-interface-name> table <route-table-name>
    
    ip rule add from <network-interface-address> table <route-table-name>
  Configure the parameters as follows:
  - Network interface name: Enter the name obtained in 4.
  - Route table name: Name the route table with a number.
  - Other network information: Enter the IP addresses collected in 1.
  In this example, run the following commands:
  - Primary network interface
    ip route add default via 10.0.0.1 dev eth0 table 10
    
    ip route add 10.0.0.0/24 dev eth0 table 10
    
    ip rule add from 10.0.0.115 table 10
  - Extended network interface
    ip route add default via 10.0.1.1 dev eth1 table 20
    
    ip route add 10.0.1.0/24 dev eth1 table 20
    
    ip rule add from 10.0.1.183 table 20
  If the ECS has multiple network interfaces, configure policy-based routes for all network interfaces one by one.
2. Check whether the policy-based routes are added.
  ip rule
  
  ip route show table <route-table-name-of-the-primary-network-interface>
  
  ip route show table <route-table-name-of-the-extended-network-interface>
  
  The route table name is the one configured in 5.a.
  
  In this example, run the following commands:
  
  ip rule
  
  ip route show table 10
  
  ip route show table 20
  If information similar to the following is displayed, the policy-based routes have been added.
```
[root@ecs-resource ~]# ip rule
0:      from all lookup local
32764:  from 10.0.1.183 lookup 20
32765:  from 10.0.0.115 lookup 10
32766:  from all lookup main
32767:  from all lookup default
[root@ecs-resource ~]# ip route show table 10
default via 10.0.0.1 dev eth0 
10.0.0.0/24 dev eth0 scope link 
[root@ecs-resource ~]# ip route show table 20
default via 10.0.1.1 dev eth1 
10.0.1.0/24 dev eth1 scope link 
```
3. Check whether the source and destination ECSs can communicate with each other.
  ping -I <IP-address-of-the-primary-network-interface-on-the-source-ECS> <IP-address-of-the-destination-ECS>
  
  ping -I <IP-address-of-the-extended-network-interface-on-the-source-ECS> <IP-address-of-the-destination-ECS>
  
  In this example, run the following commands:
  
  ping -I 10.0.0.115 10.0.2.12
  
  ping -I 10.0.1.183 10.0.2.12
  
  If information similar to the following is displayed, both the network interfaces of the source ECS can communicate with the destination ECS.
```
[root@ecs-resource ~]# ping -I 10.0.0.115 10.0.2.12
PING 10.0.2.12 (10.0.2.12) from 10.0.0.115 : 56(84) bytes of data.
64 bytes from 10.0.2.12: icmp_seq=1 ttl=64 time=0.775 ms
64 bytes from 10.0.2.12: icmp_seq=2 ttl=64 time=0.268 ms
64 bytes from 10.0.2.12: icmp_seq=3 ttl=64 time=0.220 ms
64 bytes from 10.0.2.12: icmp_seq=4 ttl=64 time=0.167 ms
^C
--- 10.0.2.12 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 102ms
rtt min/avg/max/mdev = 0.167/0.357/0.775/0.244 ms
[root@ecs-resource ~]# ping -I 10.0.1.183 10.0.2.12
PING 10.0.2.12 (10.0.2.12) from 10.0.1.183 : 56(84) bytes of data.
64 bytes from 10.0.2.12: icmp_seq=1 ttl=64 time=2.84 ms
64 bytes from 10.0.2.12: icmp_seq=2 ttl=64 time=0.258 ms
64 bytes from 10.0.2.12: icmp_seq=3 ttl=64 time=0.234 ms
64 bytes from 10.0.2.12: icmp_seq=4 ttl=64 time=0.153 ms
^C
--- 10.0.2.12 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 92ms
rtt min/avg/max/mdev = 0.153/0.871/2.840/1.137 ms
```
Configure persistent routes for the source ECS.
1. Run the following command to open the /etc/rc.local file:
  vi /etc/rc.local
2. Press i to enter the editing mode.
3. Add the following content to the end of the file:
```
# check eth0 
for ((x=0; x<30; x++)); do
  if (ping -I eth0 10.0.0.1 -c 1 -W 1 >/dev/null 2>&1); then
    break
  fi
done

# Add v4 routes for eth0
ip route flush table 10
ip route add default via 10.0.0.1 dev eth0 table 10
ip route add 10.0.0.0/24 dev eth0 table 10
ip rule add from 10.0.0.115 table 10

# check eth1
for ((x=0; x<30; x++)); do
  if (ping -I eth1 10.0.1.1 -c 1 -W 1 >/dev/null 2>&1); then
    break
  fi
done

# Add v4 routes for eth1
ip route flush table 20
ip route add default via 10.0.1.1 dev eth1 table 20
ip route add 10.0.1.0/24 dev eth1 table 20
ip rule add from 10.0.1.183 table 20
# Add v4 routes for cloud-init
ip rule add to 169.254.169.254 table main
```
  The parameters are as follows:
  - check eth0: checks whether the primary network interface is started by pinging the IPv4 gateway of the subnet where the primary network interface resides. In this example, 10.0.0.1 indicates the IPv4 gateway of the subnet where primary network interface eth0 resides, -c 1 indicates that one data packet is sent at a time, and -W 1 indicates that the timeout duration is 1s and the number of retries is 30.
  - Add v4 routes for eth0: policy-based routes of the primary network interface. Set the value to be the same as that configured in 5.a.
  - check eth1: checks whether the extended network interface is started by pinging the IPv4 gateway of the subnet where the extended network interface resides. In this example, 10.0.0.1 indicates the IPv4 gateway of the subnet where extended network interface eth1 resides, -c 1 indicates that one data packet is sent at a time, and -W 1 indicates that the timeout duration is 1s and the number of retries is 30.
  - Add v4 routes for eth1: policy-based routes of the extended network interface. Set the value to be the same as that configured in 5.a.
  - Add v4 routes for cloud-init: Configure the Cloud-Init address. Set the value to be the same as that in the preceding configurations.
4. Press ESC to exit and enter :wq! to save the configuration.
5. Run the following command to assign execute permissions to the /etc/rc.local file:
  chmod +x /etc/rc.local
  
  If your operating system is Red Hat or EulerOS, run the following command after you perform 6.e:
  
  chmod +x /etc/rc.d/rc.local
6. Run the following command to restart the ECS:
  reboot
  
  Policy-based routes added to the /etc/rc.local file take effect only after the ECS is restarted. Ensure that workloads on the ECS will not be affected before restarting the ECS.
7. Repeat 5.b to 5.c to check whether the policy-based routes are added and whether the source ECS and the destination ECS can communicate with each other.

Configuring IPv6 Policy-based Routes for a CentOS ECS

Collect the ECS network information required for configuring policy-based routes.

For details, see Collecting ECS Network Information.

**Table 2** CentOS ECS using IPv6
ECS	Primary Network Interface	Extended Network Interface
Source	IPv4 address: 10.0.0.102 IPv6 address: 2407:c080:1200:1dd8:859c:e5d5:8b3d:a2d9 IPv6 subnet: 2407:c080:1200:1dd8::/64 IPv6 subnet gateway: 2407:c080:1200:1dd8::1	IPv4 address: 10.0.1.191 IPv6 address: 2407:c080:1200:1a9c:7cc0:63b5:8e65:4dd8 IPv6 subnet: 2407:c080:1200:1a9c::/64 IPv6 subnet gateway: 2407:c080:1200:1a9c::1
Destination	IPv4 address: 10.0.2.3 IPv6 address: 2407:c080:1200:1dd9:16a7:fe7a:8f71:7044	N/A

Check whether the ECSs have IPv6 enabled and have IPv6 addresses.

Perform this step for both the source and destination ECSs to ensure that the ECSs have IPv6 addresses. Otherwise, the ECSs cannot communicate with each other using IPv6 addresses.

ECSs in this example run CentOS 8.0 (64-bit). For details about how to assign IPv6 addresses for ECSs running other OSs, see Dynamically Assigning IPv6 Addresses.

Run the following command to check whether the ECS has IPv6 addresses:

ip addr

In the following command output, eth0 and eth1 are the network interfaces of the ECS. Each network interface has one inet6 followed by an IP address starting with fe80. This indicates that the ECS has IPv6 enabled but has not been assigned IPv6 addresses. In this case, perform 3.b to 3.g to assign IPv6 addresses.

[root@ecs-resource ~]# ip addr
...
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether fa:16:3e:22:22:88 brd ff:ff:ff:ff:ff:ff
    inet 10.0.0.102/24 brd 10.0.0.255 scope global dynamic noprefixroute eth0
       valid_lft 107943256sec preferred_lft 107943256sec
    inet6 fe80::f816:3eff:fe22:2288/64 scope link 
       valid_lft forever preferred_lft forever
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether fa:16:3e:22:23:e1 brd ff:ff:ff:ff:ff:ff
    inet 10.0.1.191/24 brd 10.0.1.255 scope global dynamic noprefixroute eth1
       valid_lft 107943256sec preferred_lft 107943256sec
    inet6 fe80::f816:3eff:fe22:23e1/64 scope link 
       valid_lft forever preferred_lft forever

Query the network interface names of the source ECS:

ifconfig

Search for the network interface names based on IP addresses.

The primary network interface address is 10.0.0.102, and its name is eth0.
The extended network interface address is 10.0.1.191, and its name is eth1.

[root@ecs-resource ~]# ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 10.0.0.102  netmask 255.255.255.0  broadcast 10.0.0.255
        inet6 fe80::f816:3eff:fe22:2288  prefixlen 64  scopeid 0x20<link>
        ether fa:16:3e:22:22:88  txqueuelen 1000  (Ethernet)
        RX packets 135116  bytes 132321802 (126.1 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 60963  bytes 23201005 (22.1 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

eth1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 10.0.1.191  netmask 255.255.255.0  broadcast 10.0.1.255
        inet6 fe80::f816:3eff:fe22:23e1  prefixlen 64  scopeid 0x20<link>
        ether fa:16:3e:22:23:e1  txqueuelen 1000  (Ethernet)
        RX packets 885  bytes 97676 (95.3 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 47  bytes 4478 (4.3 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

Configure the ifcfg file of the primary network interface.
1. Run the following command to open the ifcfg file of the primary network interface:
  vi /etc/sysconfig/network-scripts/ifcfg-Primary network interface name
  
  The name of the primary network interface is obtained in 3.b.
  
  In this example, run the following command:
  
  vi /etc/sysconfig/network-scripts/ifcfg-eth0
2. Press i to enter the editing mode.
3. Add the following content to the end of the file:
```
IPV6INIT="yes"
DHCPV6C="yes"
```
4. Press ESC to exit and enter :wq! to save the configuration.
Configure the ifcfg file of the extended network interface.
1. Run the following command to open the ifcfg file of the extended network interface:
  vi /etc/sysconfig/network-scripts/ifcfg-Extended network interface name
  
  The name of the extended network interface is obtained in 3.b.
  
  In this example, run the following command:
  
  vi /etc/sysconfig/network-scripts/ifcfg-eth1
2. Press i to enter the editing mode.
3. Add the following content to the end of the file:
```
IPV6INIT="yes"
DHCPV6C="yes"
```
4. Press ESC to exit and enter :wq! to save the configuration.
Edit the /etc/sysconfig/network file.
1. Run the following command to open the /etc/sysconfig/network file:
  vi /etc/sysconfig/network
2. Press i to enter the editing mode.
3. Add the following content to the end of the file:
```
NETWORKING_IPV6="yes"
```
4. Press ESC to exit and enter :wq! to save the configuration.
Run the following command to restart the network service for the configuration to be applied:
systemctl restart NetworkManager

Run the following command to check whether the ECS has IPv6 addresses:

ip addr

In the following command output, each network interface has one more inet6 followed by an IP address starting with 2407 in addition to the one followed by an IP address starting with fe80. In this case, the ECS has been assigned IPv6 addresses.

[root@ecs-resource ~]# ip addr
...
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether fa:16:3e:22:22:88 brd ff:ff:ff:ff:ff:ff
    inet 10.0.0.102/24 brd 10.0.0.255 scope global dynamic noprefixroute eth0
       valid_lft 107999994sec preferred_lft 107999994sec
    inet6 2407:c080:1200:1dd8:859c:e5d5:8b3d:a2d9/128 scope global dynamic noprefixroute 
       valid_lft 7195sec preferred_lft 7195sec
    inet6 fe80::f816:3eff:fe22:2288/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether fa:16:3e:22:23:e1 brd ff:ff:ff:ff:ff:ff
    inet 10.0.1.191/24 brd 10.0.1.255 scope global dynamic noprefixroute eth1
       valid_lft 107999994sec preferred_lft 107999994sec
    inet6 2407:c080:1200:1a9c:7cc0:63b5:8e65:4dd8/128 scope global dynamic noprefixroute 
       valid_lft 7198sec preferred_lft 7198sec
    inet6 fe80::f816:3eff:fe22:23e1/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever

Log in to the source ECS and check whether it can use its primary network interface to communicate with the destination ECS:

ping6 -I <IP-address-of-the-primary-network-interface-on-the-source-ECS> <IP-address-of-the-destination-ECS>

In this example, run the following command:

ping6 -I 2407:c080:1200:1dd8:859c:e5d5:8b3d:a2d9 2407:c080:1200:1dd9:16a7:fe7a:8f71:7044

If information similar to the following is displayed, the source ECS can use its primary network interface to communicate with the destination ECS.

[root@ecs-resource ~]# ping6 -I 2407:c080:1200:1dd8:859c:e5d5:8b3d:a2d9 2407:c080:1200:1dd9:16a7:fe7a:8f71:7044
PING 2407:c080:1200:1dd9:16a7:fe7a:8f71:7044(2407:c080:1200:1dd9:16a7:fe7a:8f71:7044) from 2407:c080:1200:1dd8:859c:e5d5:8b3d:a2d9 : 56 data bytes
64 bytes from 2407:c080:1200:1dd9:16a7:fe7a:8f71:7044: icmp_seq=1 ttl=64 time=0.635 ms
64 bytes from 2407:c080:1200:1dd9:16a7:fe7a:8f71:7044: icmp_seq=2 ttl=64 time=0.320 ms
64 bytes from 2407:c080:1200:1dd9:16a7:fe7a:8f71:7044: icmp_seq=3 ttl=64 time=0.287 ms
64 bytes from 2407:c080:1200:1dd9:16a7:fe7a:8f71:7044: icmp_seq=4 ttl=64 time=0.193 ms
^C
--- 2407:c080:1200:1dd9:16a7:fe7a:8f71:7044 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3074ms
rtt min/avg/max/mdev = 0.193/0.358/0.635/0.167 ms

Before configuring policy-based routes, ensure that the source ECS can use its primary network interface to communicate with the destination ECS.

Log in to the source ECS and configure temporary routes for the ECS.

Temporary routes are applied immediately but are lost after ECS restarts. To avoid network disruptions, perform 6 to configure persistent routes instead.
1. Configure policy-based routes for both the primary and extended network interfaces.
  - Primary network interface
    ip -6 route add default via <subnet-gateway> dev <network-interface-name> table <route-table-name>
    
    ip -6 route add <subnet-CIDR-block> dev <network-interface-name> table <route-table-name>
    
    ip -6 rule add from <network-interface-address> table <route-table-name>
  - Extended network interface
    ip -6 route add default via <subnet-gateway> dev <network-interface-name> table <route-table-name>
    
    ip -6 route add <subnet-CIDR-block> dev <network-interface-name> table <route-table-name>
    
    ip -6 rule add from <network-interface-address> table <route-table-name>
  Configure the parameters as follows:
  - Network interface name: Enter the name obtained in 3.b.
  - Route table name: Name the route table with a number.
  - Other network information: Enter the IP addresses collected in 1.
  In this example, run the following commands:
  - Primary network interface
    ip -6 route add default via 2407:c080:1200:1dd8::1 dev eth0 table 10
    
    ip -6 route add 2407:c080:1200:1dd8::/64 dev eth0 table 10
    
    ip -6 rule add from 2407:c080:1200:1dd8:859c:e5d5:8b3d:a2d9 table 10
  - Extended network interface
    ip -6 route add default via 2407:c080:1200:1a9c::1 dev eth1 table 20
    
    ip -6 route add 2407:c080:1200:1a9c::/64 dev eth1 table 20
    
    ip -6 rule add from 2407:c080:1200:1a9c:7cc0:63b5:8e65:4dd8 table 20
  If the ECS has multiple network interfaces, configure policy-based routes for all network interfaces one by one.
2. Check whether the policy-based routes are added.
  ip -6 rule
  
  ip -6 route show table <route-table-name-of-the-primary-network-interface>
  
  ip -6 route show table <route-table-name-of-the-extended-network-interface>
  
  The route table name is the one configured in 5.a.
  
  In this example, run the following commands:
  
  ip -6 rule
  
  ip -6 route show table 10
  
  ip -6 route show table 20
  If information similar to the following is displayed, the policy-based routes have been added.
```
[root@ecs-resource ~]# ip -6 rule
0:      from all lookup local
32764:  from 2407:c080:1200:1a9c:7cc0:63b5:8e65:4dd8 lookup 20
32765:  from 2407:c080:1200:1dd8:859c:e5d5:8b3d:a2d9 lookup 10
32766:  from all lookup main
[root@ecs-resource ~]# ip -6 route show table 10
2407:c080:1200:1dd8::/64 dev eth0 metric 1024 pref medium
default via 2407:c080:1200:1dd8::1 dev eth0 metric 1024 pref medium
[root@ecs-resource ~]# ip -6 route show table 20
2407:c080:1200:1a9c::/64 dev eth1 metric 1024 pref medium
default via 2407:c080:1200:1a9c::1 dev eth1 metric 1024 pref medium
```
3. Check whether the source and destination ECSs can communicate with each other.
  ping -6 -I <IP-address-of-the-primary-network-interface-on-the-source-ECS> <IP-address-of-the-destination-ECS>
  
  ping -6 -I <IP-address-of-the-extended-network-interface-on-the-source-ECS> <IP-address-of-the-destination-ECS>
  
  In this example, run the following commands:
  
  ping -6 -I 2407:c080:1200:1dd8:859c:e5d5:8b3d:a2d9 2407:c080:1200:1dd9:16a7:fe7a:8f71:7044
  
  ping -6 -I 2407:c080:1200:1a9c:7cc0:63b5:8e65:4dd8 2407:c080:1200:1dd9:16a7:fe7a:8f71:7044
  If information similar to the following is displayed, both the network interfaces of the source ECS can communicate with the destination ECS.
```
[root@ecs-resource ~]# ping -6 -I 2407:c080:1200:1dd8:859c:e5d5:8b3d:a2d9 2407:c080:1200:1dd9:16a7:fe7a:8f71:7044
PING 2407:c080:1200:1dd9:16a7:fe7a:8f71:7044(2407:c080:1200:1dd9:16a7:fe7a:8f71:7044) from 2407:c080:1200:1dd8:859c:e5d5:8b3d:a2d9 : 56 data bytes
64 bytes from 2407:c080:1200:1dd9:16a7:fe7a:8f71:7044: icmp_seq=1 ttl=64 time=0.770 ms
64 bytes from 2407:c080:1200:1dd9:16a7:fe7a:8f71:7044: icmp_seq=2 ttl=64 time=0.295 ms
64 bytes from 2407:c080:1200:1dd9:16a7:fe7a:8f71:7044: icmp_seq=3 ttl=64 time=0.245 ms
^C
--- 2407:c080:1200:1dd9:16a7:fe7a:8f71:7044 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2080ms
rtt min/avg/max/mdev = 0.245/0.436/0.770/0.237 ms
[root@ecs-resource ~]# ping -6 -I 2407:c080:1200:1a9c:7cc0:63b5:8e65:4dd8 2407:c080:1200:1dd9:16a7:fe7a:8f71:7044
PING 2407:c080:1200:1dd9:16a7:fe7a:8f71:7044(2407:c080:1200:1dd9:16a7:fe7a:8f71:7044) from 2407:c080:1200:1a9c:7cc0:63b5:8e65:4dd8 : 56 data bytes
64 bytes from 2407:c080:1200:1dd9:16a7:fe7a:8f71:7044: icmp_seq=1 ttl=64 time=0.922 ms
64 bytes from 2407:c080:1200:1dd9:16a7:fe7a:8f71:7044: icmp_seq=2 ttl=64 time=0.307 ms
64 bytes from 2407:c080:1200:1dd9:16a7:fe7a:8f71:7044: icmp_seq=3 ttl=64 time=0.174 ms
^C
--- 2407:c080:1200:1dd9:16a7:fe7a:8f71:7044 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2059ms
rtt min/avg/max/mdev = 0.174/0.467/0.922/0.326 ms
```
Configure persistent routes for the source ECS.
1. Run the following command to open the /etc/rc.local file:
  vi /etc/rc.local
2. Press i to enter the editing mode.
3. Add the following content to the end of the file:
```
# check eth0 
for ((x=0; x<30; x++)); do
  if (ping6 -I eth0 2407:c080:1200:1dd8::1 -c 1 -W 1 >/dev/null 2>&1); then
    break
  fi
done

# Add v6 routes for eth0
ip -6 route flush table 10
ip -6 route add default via 2407:c080:1200:1dd8::1 dev eth0 table 10
ip -6 route add 2407:c080:1200:1dd8::/64 dev eth0 table 10
ip -6 rule add from 2407:c080:1200:1dd8:859c:e5d5:8b3d:a2d9 table 10

# check eth1
for ((x=0; x<30; x++)); do
  if (ping6 -I eth1 2407:c080:1200:1a9c::1 -c 1 -W 1 >/dev/null 2>&1); then
    break
  fi
done

# Add v6 routes for eth1
ip -6 route flush table 20
ip -6 route add default via 2407:c080:1200:1a9c::1 dev eth1 table 20
ip -6 route add 2407:c080:1200:1a9c::/64 dev eth1 table 20
ip -6 rule add from 2407:c080:1200:1a9c:7cc0:63b5:8e65:4dd8 table 20
```
  The parameters are as follows:
  - check eth0: checks whether the primary network interface is started by pinging the IPv6 gateway of the subnet where the primary network interface resides. In this example, 2407:c080:1200:1dd8::1 indicates the IPv6 gateway of the subnet where primary network interface eth0 resides, -c 1 indicates that one data packet is sent at a time, and -W 1 indicates that the timeout duration is 1s and the number of retries is 30.
  - Add v6 routes for eth0: policy-based routes of the primary network interface. Set the value to be the same as that configured in 5.a.
  - check eth1 : checks whether the extended network interface is started by pinging the IPv6 gateway of the subnet where the extended network interface resides. In this example, 2407:c080:1200:1a9c::1 indicates the IPv6 gateway of the subnet where extended network interface eth1 resides, -c 1 indicates that one data packet is sent at a time, and -W 1 indicates that the timeout duration is 1s and the number of retries is 30.
  - Add v6 routes for eth1: policy-based routes of the extended network interface. Set the value to be the same as that configured in 5.a.
4. Press ESC to exit and enter :wq! to save the configuration.
5. Run the following command to assign execute permissions to the /etc/rc.local file:
  chmod +x /etc/rc.local
  
  If your operating system is Red Hat or EulerOS, run the following command after you perform 6.e:
  
  chmod +x /etc/rc.d/rc.local
6. Run the following command to restart the ECS:
  reboot
  
  Policy-based routes added to the /etc/rc.local file take effect only after the ECS is restarted. Ensure that workloads on the ECS will not be affected before restarting the ECS.
7. Repeat 5.b to 5.c to check whether the policy-based routes are added and whether the source ECS and the destination ECS can communicate with each other.

Parent Topic: Configuring Policy-based Routes for an ECS with Multiple Network Interfaces

Previous topic: Collecting ECS Network Information

Next topic: Configuring IPv4 and IPv6 Policy-based Routes for a Linux ECS with Multiple Network Interfaces (Ubuntu)

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