Introduction
This chapter introduces how Border-PxTR-13 registers
the external IP prefix 172.16.30.0/24 received as a BGP update from vEdge-1 to
MapSrv-22 using LISP Map-register messages. Chapter 2 explains the LISP
RLOC-to-EID mapping process in detail so this chapter just briefly recaps the
operation. Figure 5-1 illustrates the overall process. vEdge-1 sends a BGP
Update message where it describes the NLRI for prefix 172.16.30.0/24.
Border-PxTR-13 first imports the information into the LISP processes. Next, it
sends a LISP Map-Register message to MapSrv-22. In addition to IP prefix
information, the Map-Register message carries Locator Record information that
describes the destination IP address used in the outer IP header (tunnel
header) when devices route IP packets towards the advertised subnet.
Figure 5-1: Overall Control-Plane Operation: OMP to LISP
Phases 1-2: OMP to BGP in vEdge-1
Capture 5-1 shows the BGP Update message from vEdge-1
to Border-PxTR-13. The Route-Origin BGP extended community attribute carries
the Site-Id of advertising device vEdge-1. BGP uses this attribute for
preventing other edge devices from advertising the route back to SD-WAN edge
devices.
Internet Protocol Version
4, Src: 172.16.10.1, Dst: 172.16.10.13
Transmission Control
Protocol, Src Port: 51909, Dst Port: 179, Seq: 39, Ack: 39, Len: 66
Border Gateway Protocol - UPDATE
Message
Marker: ffffffffffffffffffffffffffffffff
Length: 66
Type: UPDATE Message (2)
Withdrawn Routes Length: 0
Total Path Attribute Length: 39
Path attributes
Path Attribute - ORIGIN: INCOMPLETE
Path Attribute - AS_PATH: 65100
Path Attribute - NEXT_HOP: 172.16.10.1
Path Attribute - MULTI_EXIT_DISC: 1000
Path Attribute - EXTENDED_COMMUNITIES
Flags: 0xc0, Optional, Transitive,
Complete
Type Code: EXTENDED_COMMUNITIES
(16)
Length: 8
Carried extended communities: (1
community)
Route Origin: 0:10 [Transitive
2-Octet AS-Specific]
Type: Transitive 2-Octet
AS-Specific (0x00)
Subtype (AS2): Route Origin
(0x03)
2-Octet AS: 0
4-Octet AN: 10
Network Layer Reachability Information
(NLRI)
172.16.30.0/24
NLRI prefix length: 24
NLRI prefix: 172.16.30.0
Capture
5-1:
BGP Update from vEdge-1 to
Border-PxTR-13.
Phase 3: LISP Map-Register to MapSrv-22 from Border-PxTR-13
Capture 5-1 shows the LISP Map-Register message from
Border-PxTR-13 to MapSrv-22. This message is the first one and that is why it
uses unreliable transport protocol UDP. The mapping process follows the basic
procedures where Border-PxTR-13 starts a TCP three-way handshake process to
open the TCP connection with MapSrv-22. I have explained the complete
Map-Register process in chapter 2. If we compare the LISP EID-to-RLOC
registration processes to the operation of OMP, we can notice lots of
similarities. The later highlighted section in capture 5-2 shows the Locator
Record 1. It describes the public IP address used in the tunneling header as a
destination IP address. In other words, the Locator Record section describes
the location just like we describe the device location in OMP TLOC Routes
(Public IP used by device). The first highlighted section Mapping Record, in
turn, describes the IP Prefix and its LISP Instance-Id (Virtual Network) just
like OMP Service Route. The main difference is that LISP sends information
within one message while OMP uses separate messages.
Internet Protocol Version
4, Src: 192.168.0.13, Dst: 192.168.0.22
User Datagram Protocol,
Src Port: 4342, Dst Port: 4342
Locator/ID Separation
Protocol
0011 .... .... .... .... .... = Type:
Map-Register (3)
.... 1... .... .... .... .... = P bit
(Proxy-Map-Reply): Set
.... .0.. .... .... .... .... = S bit
(LISP-SEC capable): Not set
.... ..1. .... .... .... .... = I bit
(xTR-ID present): Set
.... ...0 .... .... .... .... = R bit
(Built for an RTR): Not set
.... .... 0000 0000 0000 000. = Reserved
bits: 0x0000
.... .... .... .... .... ...1 = M bit
(Want-Map-Notify): Set
Record Count: 1
Nonce: 0x54faec8822e5bc8b
Key ID: 0x0001
Authentication Data Length: 20
Authentication Data:
25292a07c6b2deac2811fdb92b9ff9e9d9e57b74
Mapping Record 1, EID Prefix: [100]
172.16.30.0/24, TTL: 1440, Action: No-Action, Authoritative
Record TTL: 1440
Locator Count: 1
EID Mask Length: 24
000. .... .... .... = Action: No-Action
(0)
...1 .... .... .... = Authoritative
bit: Set
.... .000 0000 0000 = Reserved: 0x000
0000 .... .... .... = Reserved: 0x0
.... 0000 0000 0000 = Mapping Version:
0
EID Prefix AFI: LISP Canonical Address
Format (LCAF) (16387)
EID Prefix: [100] 172.16.30.0
LCAF: Instance ID: 100, Address:
172.16.30.0
LCAF Header: 00000220000a
Instance ID: 100
Address AFI: IPv4 (1)
Address: 172.16.30.0
Locator Record 1, Local RLOC:
192.168.0.13, Reachable, Priority/Weight: 1/1, Multicast Priority/Weight: 1/1
Priority: 1
Weight: 1
Multicast Priority: 1
Multicast Weight: 1
Flags: 0x0005
AFI: IPv4 (1)
Locator: 192.168.0.13
xTR-ID: efd8cace5906016ad7c49f5f5cc352db
Site-ID: 0000000000000000
Capture
5-2:
LISP Map-Register Message from
Border-PxTR-13 to MapSrv-22.
Example 5-1 shows the VRF 100_NWKT specific BRIB entry
about subnet 172.16.30.0/24. Not that the Route-Origin extended BGP community
is encoded as Site-of-Origin (SoO).
Border-PxTR-13#sh bgp vrf 100_NWKT 172.16.30.0
BGP routing table entry
for 1:100:172.16.30.0/24, version 3
Paths: (1 available, best
#1, table 100_NWKT)
Advertised to update-groups:
2
Refresh Epoch 1
65100
172.16.10.1 (via vrf 100_NWKT) from
172.16.10.1 (10.100.100.101)
Origin incomplete, metric 1000, localpref
100, valid, external, best
Extended Community: SoO:0:10 RT:1:100
mpls labels in/out 17/nolabel
rx pathid: 0, tx pathid: 0x0
Example
5-1:
Border-PxTR-13’s BGP Table.
Example 5-2 verifies that the route is imported into
the RIB of Border-PxTR-13.
Border-PxTR-13#sh ip route vrf 100_NWKT 172.16.30.0
Routing Table: 100_NWKT
Routing entry for
172.16.30.0/24
Known via "bgp 65010", distance 20,
metric 1000
Tag 65100, type external
Redistributing via lisp
Last update from 172.16.10.1 00:07:16 ago
Routing Descriptor Blocks:
* 172.16.10.1, from 172.16.10.1, 00:07:16 ago
Route metric is 1000, traffic share count
is 1
AS Hops 1
Route tag 65100
MPLS label: none
Example
5-2:
Border-PxTR-13’s RIB.
Example 5-3 shows that Border-PxTR-13 has installed
the IP prefix 172.16.30.0/24 to its LISP process. Remember that the locator-ser
RLOC-SET1 defines the Locator IP address. You can find the RLOC-SET1
configuration from Appendix A of chapter 1.
Border-PxTR-13#show lisp instance-id 100 ipv4 database
172.16.30.0/24
LISP ETR IPv4 Mapping
Database for EID-table vrf 100_NWKT (IID 100), LSBs: 0x1
Entries total 2, no-route
0, inactive 0
172.16.30.0/24,
route-import, inherited from default locator-set RLOC-SET1
Locator
Pri/Wgt Source State
192.168.0.13 1/1
cfg-intf site-self, reachable
Example
5-3:
Border-PxTR-13’s LISP Mapping Database.
Example 5-4 shows that MapSrv-22 has installed the
information into its LISP Mapping Database.
MapSrv-22#show lisp site 172.16.30.0/24 instance-id
100
LISP Site Registration
Information
Site name: Network-Times
Allowed configured
locators: any
Requested EID-prefix:
EID-prefix: 172.16.30.0/24 instance-id 100
First registered: 00:48:51
Last registered: 00:48:32
Routing table tag: 0
Origin: Configuration, accepting more
specifics
Merge active: No
Proxy
reply: Yes
TTL: 1d00h
State: complete
Registration errors:
Authentication failures: 0
Allowed locators mismatch: 0
ETR 192.168.0.13, last registered 00:48:32,
proxy-reply, map-notify
TTL 1d00h, no merge,
hash-function sha1, nonce 0x54FAEC88-0x22E5BC8B
state complete, no
security-capability
xTR-ID
0xEFD8CACE-0x5906016A-0xD7C49F5F-0x5CC352DB
site-ID unspecified
sourced by reliable
transport
Locator Local
State Pri/Wgt Scope
192.168.0.13 yes
up 1/1 IPv4 none
Example
5-4:
MapSrv-22’s LISP Mapping Database.
In order to advertise internal IP Prefixes to
Border-PxTR-13, MapSrv-22 exports all LISP Mapping information to the BGP
process. This means that also the external IP prefix 172.16.30.0/24 will be
exported to the BGP process. For this reason, we are using route maps to permit
only the LISP domain internal networks to be advertised to Border-PxTR-13. We
can see from the example 5-5 that subnet 172.16.30.0/24 is not advertised to
any peer. You can find MapSrv-22’s configuration from the Appendix A of chapter
one.
MapSrv-22#sh ip bgp vpnv4 vrf 100_NWKT 172.16.30.0/24
BGP routing table entry
for 1:100:172.16.30.0/24, version 5
Paths: (1 available, best
#1, table 100_NWKT)
Not advertised to any peer
Refresh Epoch 1
65100
192.168.0.13 (metric 3) (via default) from
192.168.0.13 (192.168.0.13)
Origin incomplete, metric 1000, localpref
100, valid, internal, best
Extended Community: SoO:0:10 RT:1:100
mpls labels in/out nolabel/17
rx pathid: 0, tx pathid: 0x0
Example
5-5:
MapSrv-22’s BGP Table.
Summary
Figure 5-2 summarizes the End-to-End Control-Plane operation. Edge-xTR-11 learns the IP address of EP1 from the ingress GARP message (1). It sends the host-specific EID-to-RLOC information to MapSrv-22 using LISP Map-Register messages (2). LISP Mapping Server publishes mapping information only when separately asked with LISP Map-Request messages. That is why MapSrv-22 exports the information to the BGP process and advertises the aggregate 172.16.30.0/24 to Border-PxTR-13 as VPNv4 NLRI (3). The VPNv4 NLRI is needed because we need to differentiate routes belonging to separate VRFs/Tenants. Border-PxTR-13 advertises the NLRI as IPv4 Unicast route to vEdge-1 (4). It then advertises the information to vSmart as OMP Service (5), which in turn, forwards information to vEdge-2 (6). vEdge-2 exports the route to the BGP process and sends a BGP Update message to Border-Leaf-13 as IPv4 Unicast NLRI (7). Border-Leaf-13 sends the BGP Update message to its iBGP peer Spine-1 as L2VPN EVPN NLRI (8), which forwards the message retaining the Next-Hop Path Attribute installed by Border-Leaf-13 to Leaf-11 (9). As the last step, Leaf-11 installs the information to its BGP table as an L3 entry. The process is the almost same concerning EP3’s IP address propagation. The first difference is that Border-PxTR-13 doesn’t use BGP for advertising NLRI to MapSrv-22. Instead, it imports BGP routes to LISP and sends LISP Map-Register messages to MapSrv-22. Besides, MapSrv-22 doesn’t forward information to Edge-xTR-11 automatically.
Figure
5-2:
End-to-End Control-Plane Protocols.
The Next chapter goes through the whole Data-Plane
operation when EP3 in Datacenter pings EP1 in Campus Fabric.
No comments:
Post a Comment