Hello ISIS SR Team,
I am Not clear what is expected to be done wrt "supporting"
ADJ SID subTLVs {6, 8} inside TLV-22 ISIS Extended Reachability as mentioned
in RFC5305 and RFC8667. Actual ADJ SID sub-tlvs 31/32 *is not in question*.
but the supporting sub-tlvs 6/8 information is not clear and it's usage
is unknown.
Sample Config:
PTP
----- Grunt-54 ----------------------- Grunt-104 ----------- Other nodes
51.5.5.54/24 <--- PrimaryIP 51.4.4.104/24 <--- PrimaryIP
51.6.6.54/24 51.3.3.104/24
51.9.9.54/24 51.2.2.104/24
51.9.9.104/24 <---- Common IP
(secondary IP)
show isis database details wrt just TLV-22:
Metric: 10 IS-Extended Grunt-104.00
* IPv4 Interface Address: 51.5.5.54 <---------------- sub-tlv: 6
Neighbor IP Address: 51.2.2.104 <--------------------- sub-tlv: 8*
PTP-Adjacency-SID: 24104, Weight: 15, Flags: F:0 B:0 V:1 L:1 S:0 P:0
TLV-22 --- Extended ISIS Reachability
sTLV [6] - Interface IP --- RFC 5305 section 3.2
stLV [8] - Neighbor IP --- RFC 5305 section 3.3
sTLv [31/32] - ADJ SID --- RFC 8667
Sample Examples (very basic - does not talk about "64 IP addresses" on ISIS
interface ie Primary + Secondary IPs), show below:
a) http://www.linkflapping.net/post/sr-basic-configuration/
b)
https://www.segment-routing.net/tutorials/2016-09-27-segment-routing-igp-control-plane/
--- slides 52, 74
-------------------------------------------------------------------------------
Issues / Open ended Questions wrt sub-tlv 6/8 in ISIS Segment-Routing Usage:
1 - RFC-5305 says sub-tlvs 6/8 are optional.
It also says, there can be Multiple of these, no talk about "common IP"
If we do not have at least 1 commonIP then there is NO ISIS
neighborship
but why is specifying ONE of the commonIP is important ?
2. As shown above, we can have *64 IPs on an interface* .. The example
shows only 3/4.
BUT does that mean we will insert 64 sub-tlvs and fill up LSP for no
reason ?
PURE waste of LSP space and reduce route capacity.
3. Why insert only commonIP and why not any IP that is configured on the
interface ?
Our code arranges IP addresses in order of value and not in order of
Primary and Secondary IP. Hence we see lowest values entry as the
entry in current ADJ SID in LSP.
4. FP shows MAC addresses for each ADJ-SID ILM entry. What is FP supposed
to do
with ADJ SID label (means we are NOT edge router but in middle) ?
SWAP operations OR if MAC address is seen then forward the packet based
on MAC but pop ADJ SID label.
5. So what is the use of these sub-tlvs 6/8 ? even if they are NOT
commonIP ?
as CP resolves any Next Hop IP to MAC address., anyway so why Display
CommonIP ?
6. There is NO guarantee that other vendors would send these sub-tlvs as
it is
optional as per RFC 5305 unless I read 3.2 / 3.3 section wrong.
7. Not sure what all vendors do and what is the purpose of this IP. If it
is
Local usage then it should not matter.
So in short why sub-tlv 6/8 needs to be commonIP, and what is the usage. If
it is not commonIP, what is the limit 1-64 ? same as ISIS Hello Packet ?
and why are all these details not specified in RFC-8667 ?
thanks
-Waman Nawathe
-----------------------------------------------------------------------------------------------------------
Grunt-54
-----------------------------------------------------------------------------------------------------------
interface to-Grunt104
ip address 51.5.5.54/24
ip address 51.6.6.54/24 secondary
ip address 51.9.9.54/24 secondary <------------- Common IP
ipv6 enable
ipv6 address cafa:1::54/64
ip router isis 20
ipv6 router isis 20
isis network point-to-point
ip adjacency-sid index 104
label-switching
[local]Grunt-54#*show isis d d
Area 20:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
Grunt-54.00-00 * 0x0000000E 0xA468 1154 0/0/0
Area Address: 49.0011
NLPID: 0xCC 0x8E
Hostname: Grunt-54
IP Address: 54.54.54.54
IPv6 Address: cafa:1::54
Router Capability: 54.54.54.54 , D:0, S:0
Segment Routing: I:1 V:0, Global Block Base: 15000 Range: 8000
SR Local Block Base: 24000 Range: 1000
SR Algorithm:
0: Strict SPF
Node Maximum SID Depth: 2
Metric: 10 IS-Extended Grunt-104.00
<------------------------------ Does not have Common IP
IPv4 Interface Address: 51.5.5.54
Neighbor IP Address: 51.2.2.104
PTP-Adjacency-SID: 24104, Weight: 15, Flags: F:0 B:0 V:1 L:1 S:0 P:0
Metric: 0 IP-Extended 54.54.54.54/32
SR Prefix-SID: Index: 54, Algorithm: SPF, Flags: NODE PHP
Metric: 0 IP-Extended 4.4.0.0/24
Metric: 10 IP-Extended 51.5.5.0/24
Metric: 10 IP-Extended 51.6.6.0/24
Metric: 10 IP-Extended 51.9.9.0/24
Metric: 0 IP-Extended 6.6.6.0/24
Metric: 0 IP-Extended 51.1.1.0/24
Metric: 0 IP-Extended 7.7.7.0/24
Metric: 0 IP-Extended 10.13.13.0/24
Metric: 0 IP-Extended 10.40.0.0/24
Metric: 0 IP-Extended 48.1.1.0/24
Metric: 10 IPv6 cafa:1::/64
[local]Grunt-54#*show mpls ilm-table <------------------ CP
Codes: > - selected ILM, p - stale ILM, K - CLI ILM
Code In-Label Out-Label In-Intf Out-Intf Nexthop FEC
OPCODE
------ -------- --------- ------------ ------------ ----------------
-------------------- ------
> 15104 3 to-Grunt104 to-Grunt104 51.2.2.104
0.0.0.0/0 Pop
> 15054 N/A lo1 lo1 54.54.54.54
0.0.0.0/0 Pop
> 24104 N/A to-Grunt104 to-Grunt104 51.2.2.104
0.0.0.0/0 Pop
[local]Grunt-54#*fpshow table lfib
------------------------------------------:: LFIB TABLE
::-------------------------------------------------
-----------------------------------------------------------------------------------------------------------
Index | Ingress | Ingress | Entry | Egress |Next Hop IP or VCId | Egress
| Misc
| Intf | Label | Type | BindId | / Next Hop MAC | Labels
|
-----------------------------------------------------------------------------------------------------------
0 0 15054 POP 0 00:00:00:00:00:00
*11 0 24104 POP 2 A0:36:9F:88:F2:CC
<----------------- FP*
19 0 15104 POP 2 A0:36:9F:88:F2:CC
-----------------------------------------------------------------------------------------------------------
Grunt-104
-----------------------------------------------------------------------------------------------------------
[local]Grunt-104(context local)#*show run interface
context local
!
interface to-Grunt54
ip address 51.4.4.104/24
ip address 51.3.3.104/24 secondary
ip address 51.9.9.104/24 secondary <------------- Common IP
ip address 51.2.2.104/24 secondary
ipv6 enable
ipv6 address cafa:1::104/64
ip router isis 20
ipv6 router isis 20
isis network point-to-point
ip adjacency-sid index 54
label-switching
!
end
[local]Grunt-104(context local)#*show isis d d l1
Area 20:
IS-IS Level-1 Link State Database:
Grunt-104.00-00 * 0x00000037 0x391A 323 0/0/0
Area Address: 49.0011
NLPID: 0xCC 0x8E
Hostname: Grunt-104
IP Address: 171.171.171.171
IPv6 Address: cafa:1::104
Router Capability: 171.171.171.171 , D:0, S:0
Segment Routing: I:1 V:0, Global Block Base: 16000 Range: 7000
SR Local Block Base: 23000 Range: 2000
SR Algorithm:
0: Strict SPF
Node Maximum SID Depth: 2
Metric: 10 IS-Extended Grunt-54.00
IPv4 Interface Address: 51.2.2.104
<---------------------------------------
Neighbor IP Address: 51.5.5.54
PTP-Adjacency-SID: 23054, Weight: 15, Flags: F:0 B:0 V:1 L:1 S:0 P:0
Metric: 0 IP-Extended 171.171.171.171/32
SR Prefix-SID: Index: 104, Algorithm: SPF, Flags: NODE PHP
Metric: 10 IP-Extended 10.42.42.0/24
Metric: 10 IP-Extended 172.28.61.0/26
Metric: 10 IP-Extended 51.4.4.0/24
Metric: 10 IP-Extended 51.3.3.0/24
Metric: 10 IP-Extended 51.9.9.0/24
Metric: 10 IP-Extended 51.2.2.0/24
Metric: 10 IP-Extended 10.41.41.0/24
Metric: 10 IP-Extended 10.43.43.0/24
Metric: 10 IP-Extended 10.1.1.0/24
Metric: 10 IP-Extended 10.44.44.0/24
Metric: 10 IPv6 cafa:1::/64
[local]Grunt-104(context local)#*show mpls ilm-table
Codes: > - selected ILM, p - stale ILM, K - CLI ILM
Code In-Label Out-Label In-Intf Out-Intf Nexthop FEC
OPCODE
------ -------- --------- ------------ ------------ ----------------
-------------------- ------
> 23001 N/A toCisco161-f001.. toCisco161-f001.. 10.44.44.106
0.0.0.0/0 Pop
> 16104 N/A lo1 lo1 171.171.171.171
0.0.0.0/0 Pop
> 16106 3 toCisco161-f001.. toCisco161-f001.. 10.44.44.106
0.0.0.0/0 Push
> 23054 N/A to-Grunt54 to-Grunt54 51.5.5.54
0.0.0.0/0 Pop
> 16054 3 to-Grunt54 to-Grunt54 51.5.5.54
0.0.0.0/0 Pop <-----------------------CP
[local]Grunt-104(context local)#*fpshow table lfib
------------------------------------------:: LFIB TABLE
::-------------------------------------------------
-----------------------------------------------------------------------------------------------------------
Index | Ingress | Ingress | Entry | Egress |Next Hop IP or VCId | Egress
| Misc
| Intf | Label | Type | BindId | / Next Hop MAC | Labels
|
-----------------------------------------------------------------------------------------------------------
0 0 16104 POP - 171.171.171.171
920 0 23054 POP 4 A0:36:9F:A1:FA:72
1013 0 23001 POP 1 A0:36:9F:A1:F9:C2
*1031 0 16054 POP 4 A0:36:9F:A1:FA:72
<--------------------------- FP*
1032 0 16106 SWAP 1 A0:36:9F:A1:F9:C2 { 3 }
-----------------------------------------------------------------------------------------------------------
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