Example for Using XPL to Filter the Routes to Be Received and Advertised (Line-by-Line Editing)
This section provides an example for using XPL to filter the routes to be received and advertised. based on sets and route-filters in line editing mode.
Networking Requirements
- Device A advertises routes 2.2.2.0/24, 3.3.3.0/24, and 4.4.4.0/24 to Device B.
- On receipt of the three routes from Device B, Device C advertises all of them to Device E. On receipt of the three routes from Device B, Device D increases the MED value of the route 2.2.2.0/24 and advertises routes 2.2.2.0/24 and 3.3.3.0/24 to Device E. The MED of the route 2.2.2.0/24 learned from Device C is less than that of the route 2.2.2.0/24 learned from Device D. Therefore, Device E selects Device C as the egress for the traffic destined for 2.2.2.0/24.
To meet the preceding requirements, configure export or import policies. In this example, an export policy is configured on Device A, and two import policies are configured on Device E.
Device Name |
Interface |
IP Address |
|---|---|---|
Device A |
GE 3/0/0 |
1.1.5.2/24 |
Device B |
GE 3/0/0 |
1.1.5.1/24 |
Device B |
GE 3/0/1 |
1.1.4.2/24 |
Device B |
GE 3/0/2 |
1.1.3.2/24 |
Device C |
GE 3/0/1 |
1.1.1.2/24 |
Device C |
GE 3/0/2 |
1.1.3.1/24 |
Device D |
GE 3/0/1 |
1.1.2.2/24 |
Device D |
GE 3/0/2 |
1.1.4.1/24 |
Device E |
GE 3/0/1 |
1.1.2.1/24 |
Device E |
GE 3/0/2 |
1.1.1.1/24 |
Precautions
When using XPL to filter the routes to be received and advertised, note the following points:
A prefix range needs to be specified for the IPv4 prefix set as required.
IPv4 prefix set names are case-sensitive.
Configuration Roadmap
The configuration roadmap is as follows:
Configure basic BGP functions on Device A, Device B, Device C, Device D, and Device E.
Configure four static routes on Device A and import them into BGP.
Configure an export policy on Device A and check the BGP routing table of Device B.
Configure two import policies on Device E and check the BGP routing table of Device E.
Data Preparation
To complete the configuration, you need the following data:
Four static routes to be imported by Device A
AS 100 (for Device A and Device B) and AS 200 (Device C, Device D, and Device E)
Name of an IPv4 prefix set and the routes to be filtered
Procedure
- Assign an IP address to each interface. For configuration details, see Configuration Files in this section.
- Configure basic BGP functions.
# Configure Device A.
<DeviceA> system-view [~DeviceA] bgp 100 [*DeviceA-bgp] peer 1.1.5.1 as-number 100 [*DeviceA-bgp] commit [~DeviceA-bgp] quit
# Configure Device B.
<DeviceB> system-view [~DeviceB] bgp 100 [*DeviceB-bgp] peer 1.1.5.2 as-number 100 [*DeviceB-bgp] peer 1.1.3.1 as-number 200 [*DeviceB-bgp] peer 1.1.4.1 as-number 200 [*DeviceB-bgp] commit [~DeviceB-bgp] quit
# Configure Device C:
<DeviceC> system-view [~DeviceC] bgp 200 [*DeviceC-bgp] peer 1.1.1.1 as-number 200 [*DeviceC-bgp] peer 1.1.3.2 as-number 100 [*DeviceC-bgp] commit [~DeviceC-bgp] quit
# Configure Device D:
<DeviceD> system-view [~DeviceD] bgp 200 [*DeviceD-bgp] peer 1.1.2.1 as-number 200 [*DeviceD-bgp] peer 1.1.4.2 as-number 100 [*DeviceD-bgp] commit [~DeviceD-bgp] quit
# Configure Device E.
<DeviceE> system-view [~DeviceE] bgp 200 [*DeviceE-bgp] peer 1.1.1.2 as-number 200 [*DeviceE-bgp] peer 1.1.2.2 as-number 200 [*DeviceE-bgp] commit [~DeviceE-bgp] quit
- Configure four static routes on Device A and import them into BGP.
[~DeviceA] ip route-static 2.2.2.0 255.255.255.0 NULL0 [*DeviceA] ip route-static 3.3.3.0 255.255.255.0 NULL0 [*DeviceA] ip route-static 4.4.4.0 255.255.255.0 NULL0 [*DeviceA] ip route-static 5.5.5.0 255.255.255.0 NULL0 [*DeviceA] bgp 100 [*DeviceA-bgp] import-route static [*DeviceA-bgp] commit [~DeviceA-bgp] quit
# Check the BGP routing table of Device B. The following command output shows that the four static routes have been added to the BGP routing table of Device B.
[~DeviceB] display bgp routing-table BGP Local router ID is 1.1.5.1 Status codes: * - valid, > - best, d - damped, x - best external, a - add path, h - history, i - internal, s - suppressed, S - Stale Origin : i - IGP, e - EGP, ? - incomplete RPKI validation codes: V - valid, I - invalid, N - not-found Total Number of Routes: 4 Network NextHop MED LocPrf PrefVal Path/Ogn *>i 2.2.2.0/24 1.1.5.2 0 100 0 ? *>i 3.3.3.0/24 1.1.5.2 0 100 0 ? *>i 4.4.4.0/24 1.1.5.2 0 100 0 ? *>i 5.5.5.0/24 1.1.5.2 0 100 0 ?
# Check the BGP routing table of Device E. The following command output shows that two copies of the four static routes from Device C and Device D have been added to the BGP routing table of Device E.
[~DeviceE] display bgp routing-table BGP Local router ID is 1.1.1.1 Status codes: * - valid, > - best, d - damped, x - best external, a - add path, h - history, i - internal, s - suppressed, S - Stale Origin : i - IGP, e - EGP, ? - incomplete RPKI validation codes: V - valid, I - invalid, N - not-found Total Number of Routes: 8 Network NextHop MED LocPrf PrefVal Path/Ogn i 2.2.2.0/24 1.1.3.2 100 0 100? i 1.1.4.2 100 0 100? i 3.3.3.0/24 1.1.4.2 100 0 100? i 1.1.3.2 100 0 100? i 4.4.4.0/24 1.1.3.2 100 0 100? i 1.1.4.2 100 0 100? i 5.5.5.0/24 1.1.4.2 100 0 100? i 1.1.3.2 100 0 100?
- Configure an export policy on Device A.
# Configure an IPv4 prefix set named prefix1 on Device A.
[~DeviceA] xpl ip-prefix-list prefix1 [~DeviceA-xpl-pfx] 2.2.2.0 24, [~DeviceA-xpl-pfx] 3.3.3.0 24, [~DeviceA-xpl-pfx] 4.4.4.0 24 [~DeviceA-xpl-pfx] end-list [*DeviceA] commit
# Configure a route-filter named r1 on Device A, apply prefix1 to r1, and permit routes 2.2.2.0/24, 3.3.3.0/24, and 4.4.4.0/24.
[~DeviceA] xpl route-filter r1 [~DeviceA-xpl-filter] if ip route-destination in prefix1 then [~DeviceA-xpl-filter-if] approve [~DeviceA-xpl-filter-if] else [~DeviceA-xpl-filter-else] refuse [~DeviceA-xpl-filter-else] endif [~DeviceA-xpl-filter] end-filter [*DeviceA] commit
# Configure an export policy on Device A and apply r1 to the policy to filter the routes to be advertised to Device B.
<DeviceA> system-view [~DeviceA] bgp 100 [~DeviceA-bgp] peer 1.1.5.1 route-filter r1 export [*DeviceA-bgp] commit [~DeviceA-bgp] quit
# Check the BGP routing table of Device B. The following command output shows that the route 5.5.5.0/24 is not included in the BGP routing table of Device B.
[~DeviceB] display bgp routing-table BGP Local router ID is 1.1.5.1 Status codes: * - valid, > - best, d - damped, x - best external, a - add path, h - history, i - internal, s - suppressed, S - Stale Origin : i - IGP, e - EGP, ? - incomplete RPKI validation codes: V - valid, I - invalid, N - not-found Total Number of Routes: 3 Network NextHop MED LocPrf PrefVal Path/Ogn *>i 2.2.2.0/24 1.1.5.2 0 100 0 ? *>i 3.3.3.0/24 1.1.5.2 0 100 0 ? *>i 4.4.4.0/24 1.1.5.2 0 100 0 ?
- Configure two import policies on Device E.
# Configure a route-filter named appmed with a pre-defined variable to set the MED.
[~DeviceE] xpl route-filter appmed($med) [~DeviceE-xpl-filter] apply med $med [~DeviceE-xpl-filter] end-filter [*DeviceE] commit
# Configure a route-filter named r2 on Device E to permit routes 2.2.2.0/24 and 3.3.3.0/24 and use appmed to set the MED of the route 2.2.2.0/24 to 200.
[~DeviceE] xpl route-filter r2 [~DeviceE-xpl-filter] if ip route-destination in {2.2.2.0 24} then [~DeviceE-xpl-filter-if] call route-filter appmed(200) [~DeviceE-xpl-filter-if] elseif ip route-destination in {2.2.2.0 24, 3.3.3.0 24} then [~DeviceE-xpl-filter-elif] approve [~DeviceE-xpl-filter-elif] else [~DeviceE-xpl-filter-else] refuse [~DeviceE-xpl-filter-else] endif [~DeviceE-xpl-filter] end-filter [*DeviceE] commit
# Configure a route-filter named r3 on Device E to set the MED of the route 2.2.2.0/24 to 100.
[~DeviceE] xpl route-filter r3 [~DeviceE-xpl-filter] if ip route-destination in {2.2.2.0 24} then [~DeviceE-xpl-filter-if] call route-filter appmed(100) [~DeviceE-xpl-filter-if] else [~DeviceE-xpl-filter-else] approve [~DeviceE-xpl-filter-else] endif [~DeviceE-xpl-filter] end-filter [*DeviceE] commit
# Configure an import policy on Device E for the routes learned from Device D and apply r2 to the policy. In addition, configure another import policy on Device E for the routes learned from Device C and apply r3 to the policy.
<DeviceE> system-view [~DeviceE] bgp 200 [~DeviceE-bgp] peer 1.1.2.2 route-filter r2 import [*DeviceE-bgp] peer 1.1.1.2 route-filter r3 import [*DeviceE-bgp] commit [~DeviceE-bgp] quit
# Check the BGP routing table of Device E. The following command output shows that the route 4.4.4.0/24 learned from Device D is not included in the BGP routing table of Device B and that the MED values of the routes 2.2.2.0/24 learned from Device C and Device D are 100 and 200, respectively.
[~DeviceE] display bgp routing-table BGP Local router ID is 1.1.1.1 Status codes: * - valid, > - best, d - damped, x - best external, a - add path, h - history, i - internal, s - suppressed, S - Stale Origin : i - IGP, e - EGP, ? - incomplete RPKI validation codes: V - valid, I - invalid, N - not-found Total Number of Routes: 5 Network NextHop MED LocPrf PrefVal Path/Ogn i 2.2.2.0/24 1.1.4.2 200 100 0 100? i 1.1.3.2 100 100 0 100? i 3.3.3.0/24 1.1.4.2 100 0 100? i 1.1.3.2 100 0 100? i 4.4.4.0/24 1.1.3.2 100 0 100?
Configuration Files
Device A configuration file
# sysname DeviceA # interface GigabitEthernet3/0/0 undo shutdown ip address 1.1.5.2 255.255.255.0 # bgp 100 peer 1.1.5.1 as-number 100 # ipv4-family unicast undo synchronization import-route static peer 1.1.5.1 enable peer 1.1.5.1 route-filter r1 export # ip route-static 2.2.2.0 255.255.255.0 NULL0 ip route-static 3.3.3.0 255.255.255.0 NULL0 ip route-static 4.4.4.0 255.255.255.0 NULL0 ip route-static 5.5.5.0 255.255.255.0 NULL0 # xpl route-filter r1 if ip route-destination in prefix1 then approve else refuse endif end-filter # xpl ip-prefix-list prefix1 2.2.2.0 24, 3.3.3.0 24, 4.4.4.0 24 end-list # return
Device B configuration file
# sysname DeviceB # interface GigabitEthernet3/0/0 undo shutdown ip address 1.1.5.1 255.255.255.0 # interface GigabitEthernet3/0/1 undo shutdown ip address 1.1.4.2 255.255.255.0 # interface GigabitEthernet3/0/2 undo shutdown ip address 1.1.3.2 255.255.255.0 # bgp 100 peer 1.1.3.1 as-number 200 peer 1.1.4.1 as-number 200 peer 1.1.5.2 as-number 100 # ipv4-family unicast undo synchronization peer 1.1.3.1 enable peer 1.1.4.1 enable peer 1.1.5.2 enable # return
Device C configuration file
# sysname DeviceC # interface GigabitEthernet3/0/1 undo shutdown ip address 1.1.1.2 255.255.255.0 # interface GigabitEthernet3/0/2 undo shutdown ip address 1.1.3.1 255.255.255.0 # bgp 200 peer 1.1.1.1 as-number 200 peer 1.1.3.2 as-number 100 # ipv4-family unicast undo synchronization peer 1.1.1.1 enable peer 1.1.3.2 enable # return
Device D configuration file
# sysname DeviceD # interface GigabitEthernet3/0/1 undo shutdown ip address 1.1.2.2 255.255.255.0 # interface GigabitEthernet3/0/2 undo shutdown ip address 1.1.4.1 255.255.255.0 # bgp 200 peer 1.1.2.1 as-number 200 peer 1.1.4.2 as-number 100 # ipv4-family unicast undo synchronization peer 1.1.2.1 enable peer 1.1.4.2 enable # return
Device E configuration file
# sysname DeviceE # interface GigabitEthernet3/0/1 undo shutdown ip address 1.1.2.1 255.255.255.0 # interface GigabitEthernet3/0/2 undo shutdown ip address 1.1.1.1 255.255.255.0 # bgp 200 peer 1.1.1.2 as-number 200 peer 1.1.2.2 as-number 200 # ipv4-family unicast undo synchronization peer 1.1.1.2 enable peer 1.1.1.2 route-filter r3 import peer 1.1.2.2 enable peer 1.1.2.2 route-filter r2 import # xpl route-filter appmed($med) apply med $med end-filter # xpl route-filter r2 if ip route-destination in {2.2.2.0 24} then call route-filter appmed(200) elseif ip route-destination in {2.2.2.0 24, 3.3.3.0 24} then approve else refuse endif end-filter # xpl route-filter r3 if ip route-destination in {2.2.2.0 24} then call route-filter appmed(100) else approve endif end-filter # return
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