Last updated on September 13, 2020 by Sarmed Rahman
In the previous tutorials, we demonstrated how we can set up a full-fledged BGP router and configure IPv4 prefix filtering with Quagga. In this tutorial, we are going to show you how we can set up IPv6 BGP peering and advertise IPv6 prefixes through BGP. We will also demonstrate how we can filter IPv6 prefixes advertised or received by using
For this tutorial, we will be considering the following topology.
B want to establish an IPv6 BGP peering between them. Their IPv6 and AS information is as follows.
If Quagga has not already been installed, we can install it using
# yum install quagga
On CentOS/RHEL 7, the default SELinux policy, which prevents
/usr/sbin/zebra from writing to its configuration directory, can interfere with the setup procedure we are going to describe. Thus we want to disable this policy as follows. Skip this step if you are using CentOS/RHEL 6.
# setsebool -P zebra_write_config 1
After installation, we start the configuration process by creating the zebra/bgpd configuration files.
# cp /usr/share/doc/quagga-XXXXX/zebra.conf.sample /etc/quagga/zebra.conf # cp /usr/share/doc/quagga-XXXXX/bgpd.conf.sample /etc/quagga/bgpd.conf
Next, enable auto-start of these services.
# service zebra start; service bgpd start # chkconfig zebra on; chkconfig bgpd on
# systemctl start zebra; systemctl start bgpd # systemctl enable zebra; systmectl enable bgpd
Quagga provides a built-in shell called
vtysh, whose interface is similar to those of major router vendors such as Cisco or Juniper. Launch
vtysh command shell:
The prompt will be changed to:
In the rest of the tutorials, these prompts indicate that you are inside
vtysh shell of either router.
Let's configure the log file for Zebra, which will be helpful for debugging.
First, enter the global configuration mode by typing:
router-a# configure terminal
The prompt will be changed to:
Now specify log file location. Then exit the configuration mode:
router-a(config)# log file /var/log/quagga/quagga.log router-a(config)# exit
Save configuration permanently by:
Let's now configure the IP addresses for Quagga's physical interfaces.
First, we check the available interfaces from inside
router-a# show interfaces
Interface eth0 is up, line protocol detection is disabled ## OUTPUT TRUNCATED ### Interface eth1 is up, line protocol detection is disabled ## OUTPUT TRUNCATED ##
Now we assign necessary IPv6 addresses.
router-a# conf terminal router-a(config)# interface eth0 router-a(config-if)# ipv6 address 2001:db8:3::1/64 router-a(config-if)# interface eth1 router-a(config-if)# ipv6 address 2001:db8:1::1/64
We use the same method to assign IPv6 addresses to router-
B. I am summarizing the configuration below.
router-b# show running-config
interface eth0 ipv6 address 2001:db8:3::2/64 interface eth1 ipv6 address 2001:db8:2::1/64
eth0 interface of both routers are in the same subnet, i.e.,
2001:DB8:3::/64, you should be able to ping from one router to another. Make sure that you can ping successfully before moving on to the next step.
router-a# ping ipv6 2001:db8:3::2
PING 2001:db8:3::2(2001:db8:3::2) 56 data bytes 64 bytes from 2001:db8:3::2: icmp_seq=1 ttl=64 time=3.20 ms 64 bytes from 2001:db8:3::2: icmp_seq=2 ttl=64 time=1.05 ms
In this section, we will configure IPv6 BGP between the two routers. We start by specifying BGP neighbors in router-A.
router-a# conf t router-a(config)# router bgp 100 router-a(config-router)# no auto-summary router-a(config-router)# no synchronization router-a(config-router)# neighbor 2001:DB8:3::2 remote-as 200
Next, we define the address family for IPv6. Within the address family section, we will define the network to be advertised, and activate the neighbors as well.
router-a(config-router)# address-family ipv6 router-a(config-router-af)# network 2001:DB8:1::/48 router-a(config-router-af)# neighbor 2001:DB8:3::2 activate
We will go through the same configuration for router-
B. I'm providing the summary of the configuration.
router-b# conf t router-b(config)# router bgp 200 router-b(config-router)# no auto-summary router-b(config-router)# no synchronization router-b(config-router)# neighbor 2001:DB8:3::1 remote-as 100 router-b(config-router)# address-family ipv6 router-b(config-router-af)# network 2001:DB8:2::/48 router-b(config-router-af)# neighbor 2001:DB8:3::1 activate
If all goes well, an IPv6 BGP session should be up between the two routers. If not already done, please make sure that necessary ports (TCP
179) are open in your firewall.
We can check IPv6 BGP session information using the following commands.
router-a# show bgp ipv6 unicast summary
router-a# show bgp ipv6 neighbors <neighbor-IPv6-address> advertised-routes
router-a# show bgp ipv6 neighbors <neighbor-IPv6-address> routes
As we can see from the above output, the routers are advertising their full
/48 IPv6 prefix. For demonstration purposes, we will consider the following requirements.
Bwill advertise one
/56prefix, as well as one full
Awill accept any IPv6 prefix owned by service provider
B, which has a netmask length between
We are going to filter the prefix as required, using
route-map in router-
B is advertising only one
/48 prefix. We will modify router-
B's BGP configuration so that it advertises additional
/64 prefixes as well.
router-b# conf t router-b(config)# router bgp 200 router-b(config-router)# address-family ipv6 router-b(config-router-af)# network 2001:DB8:2::/56 router-b(config-router-af)# network 2001:DB8:2::/64
We will verify that all prefixes are received at router-
Great! As we are receiving all prefixes in router-
A, we will move forward and create
route-map entries to filter these prefixes.
As described in the previous tutorial,
prefix-list is a mechanism that is used to match an IP address prefix with a subnet length. Once a matched prefix is found, we can apply filtering or other actions to the matched prefix. To meet our requirements, we will go ahead and create a necessary
prefix-list entry in router-
router-a# conf t router-a(config)# ipv6 prefix-list FILTER-IPV6-PRFX permit 2001:DB8:2::/56 le 64
The above commands will create a
prefix-list entry named
FILTER-IPV6-PRFX which will match any prefix in the
2001:DB8:2:: pool with a netmask between
Now that the
prefix-list entry is created, we will create a corresponding
route-map rule which uses the
router-a# conf t router-a(config)# route-map FILTER-IPV6-RMAP permit 10 router-a(config-route-map)# match ipv6 address prefix-list FILTER-IPV6-PRFX
The above commands will create a
route-map rule named
FILTER-IPV6-RMAP. This rule will permit IPv6 addresses matched by the
FILTER-IPV6-PRFX that we have created earlier.
Remember that a
route-map rule is only effective when it is applied to a neighbor or an interface in a certain direction. We will apply the
route-map in the BGP neighbor configuration. As the filter is meant for inbound prefixes, we apply the
route-map in the inbound direction.
router-a# conf t router-a(config)# router bgp 100 router-a(config-router)# address-family ipv6 router-a(config-router-af)# neighbor 2001:DB8:3::2 route-map FILTER-IPV6-RMAP in
Now when we check the routes received at router-
A, we should see only two prefixes that are allowed.
Note: You may need to reset the BGP session for the
route-map to take effect.
All IPv6 BGP sessions can be restarted using the following command:
router-a# clear bgp ipv6 *
I am summarizing the configuration of both routers so you get a clear picture at a glance.
To sum up, this tutorial focused on how to set up BGP peering and filtering using IPv6. We showed how to advertise IPv6 prefixes to a neighboring BGP router, and how to filter the prefixes advertised or received are advertised. Note that the process described in this tutorial may affect production networks of a service provider, so please use caution.
Hope this helps.
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