network-freak

Wednesday, March 18, 2026

Implemeting SR-MPLS Tunnel over IPV6 Network Core in Nokia 7750 SR

SR MPLS over Ipv6 Core network same as IPV4 because it uses mpls label for to deliver the packets end to end. SR MPLS will be on top on IPV6 Core. We can only use IPV6 without requirement of MPLS that concept is SRV6, SRV6 uses IPv6 + SRH to delivery the packet end to end. We will explore more on SRV6 in our upcoming blog

Lets prepare the IPV6 address and prepare them to enable IPV6 end to end.

Configured the router's interface with IPV6 address

Enabling ISIS to advertise the IPV6 capabilities to the neighbour routers

Enabling cspf for ipv6

/configure router isis 1 traffic-engineering-option ipv6

Enabling IPv6 routeing within mt0

/configure router isis 1 ipv6-routing native

/configure router

segment-routing

sr-mpls

prefix-sids "system"

ipv6-sid index 81

exit

ISIS Database:

*A:PE1# show router isis 1 database level 2 PE1.00-00

===============================================================================
Rtr Base ISIS Instance 1 Database
===============================================================================
LSP ID                                  Sequence Checksum Lifetime Attributes
-------------------------------------------------------------------------------

Displaying Level 2 database
-------------------------------------------------------------------------------
PE1.00-00                               0xcb1     0xcdce   1138     L1L2
Level (2) LSP Count : 1
===============================================================================
*A:PE1# show router isis 1 database level 2 PE1.00-00 detail

===============================================================================
Rtr Base ISIS Instance 1 Database (detail)
===============================================================================

Displaying Level 2 database
-------------------------------------------------------------------------------
LSP ID    : PE1.00-00                                   Level     : L2
Sequence : 0xcb1                  Checksum : 0xcdce   Lifetime : 1135
Version   : 1                      Pkt Type : 20       Pkt Ver   : 1
Attributes: L1L2                   Max Area : 3        Alloc Len : 1492
SYS ID    : 0010.0000.0001         SysID Len : 6        Used Len : 544

TLVs :
Area Addresses:
    Area Address : (3) 49.0001
Supp Protocols:
    Protocols     : IPv4
    Protocols     : IPv6
IS-Hostname   : PE1
Router ID   :
    Router ID   : 1.0.0.1
TE Router ID v6 :
    Router ID   : fd00::1
Router Cap : 1.0.0.1, D:0, S:0
    TE Node Cap : B E M P
    SR Cap: IPv4 MPLS-IPv6
       SRGB Base:20000, Range:100
    SR Alg: metric based SPF, 129, 130
    Node MSD Cap: BMI : 12 ERLD : 15
    FAD Sub-Tlv:
        Flex-Algorithm   : 129
        Metric-Type      : delay
        Calculation-Type : 0
        Priority         : 100
        Flags: M
    FAD Sub-Tlv:
        Flex-Algorithm   : 130
        Metric-Type      : igp
        Calculation-Type : 0
        Priority         : 100
        Flags: M
        Include Any Admin Group: 0x100000
I/F Addresses :
    I/F Address   : 1.0.0.1
    I/F Address   : 192.1.1.1
    I/F Address   : 10.1.5.1
    I/F Address   : 10.1.21.1
    I/F Address   : 192.168.0.2
I/F Addresses IPv6 :
    IPv6 Address    : fd00::1
    IPv6 Address    : fd00:10:1:2::1
    IPv6 Address    : fd00:10:1:11::1
    IPv6 Address    : fd00:10:5:1::1
TE IS Nbrs   :
    Nbr   : PE5.01
    Default Metric : 10
    Sub TLV Len     : 59
    IF Addr   : 10.1.5.1
    IPv6 Addr : fd00:10:5:1::1
    TE APP LINK ATTR    :
      SABML-flag:Non-Legacy SABM-flags: S
        MaxLink BW: 10000000 kbps
    TE APP LINK ATTR    :
      SABML-flag:Non-Legacy SABM-flags:   X
        Admin Grp : 0x100000
    LAN-Adj-SID: 00 10 00 00 00 05 Flags:v4VL Weight:0 Label:524272
TE IS Nbrs   :
    Nbr   : PE2.02
    Default Metric : 10
    Sub TLV Len     : 61
    IF Addr   : 10.1.21.1
    IPv6 Addr : fd00:10:1:2::1
    TE APP LINK ATTR    :
      SABML-flag:Non-Legacy SABM-flags: S
        MaxLink BW: 10000000 kbps
    LAN-Adj-SID: 00 10 00 00 00 02 Flags:v4VL Weight:0 Label:524273
    LAN-Adj-SID: 00 10 00 00 00 02 Flags:v6VL Weight:0 Label:524286
TE IS Nbrs   :
    Nbr   : ASBR1.03
    Default Metric : 10
    Sub TLV Len     : 48
    IF Addr   : 192.1.1.1
    IPv6 Addr : fd00:10:1:11::1
    TE APP LINK ATTR    :
      SABML-flag:Non-Legacy SABM-flags: S
        MaxLink BW: 10000000 kbps
    LAN-Adj-SID: 01 10 00 00 00 01 Flags:v4VL Weight:0 Label:524275
TE IP Reach   :
    Default Metric : 10
    Control Info:    , prefLen 24
    Prefix   : 192.168.0.0
    Default Metric : 10
    Control Info:    , prefLen 24
    Prefix   : 192.1.1.0
    Default Metric : 10
    Control Info:    , prefLen 24
    Prefix   : 10.1.5.0
    Default Metric : 10
    Control Info:    , prefLen 24
    Prefix   : 10.1.21.0
    Default Metric : 0
    Control Info:   S, prefLen 32
    Prefix   : 1.0.0.1
    Sub TLV   :
      Prefix-SID Index:11, Algo:0, Flags:NnP
IPv6 Reach:
    Metric: ( IS) 0
    Prefix   : fd00::1/128
    Sub TLV   :
      Prefix-SID Index:71, Algo:0, Flags:NnP
    Metric: ( I ) 10
    Prefix   : fd00:10:1:2::/64
    Metric: ( I ) 10
    Prefix   : fd00:10:1:11::/64
    Metric: ( I ) 10
    Prefix   : fd00:10:5:1::/64
Level (2) LSP Count : 1

Enabling SR-TE LSP with IPv6

            lsp "tope3-ipv6" sr-te
                to fd00::3
                path-computation-method local-cspf
                metric-type te
                max-sr-labels 5 additional-frr-labels 2
                primary "local-cspf"
                exit
                no shutdown
            exit
            no shutdown

*A:PE5# show router mpls sr-te-lsp family ipv6 detail

=====================================================================

MPLS SR-TE LSPs (Originating) (Detail)

=====================================================================

Legend : + - Inherited

=====================================================================

Type : Originating

---------------------------------------------------------------------

LSP Name : tope3-ipv6

LSP Type : SrTeLsp LSP Tunnel ID : 3

LSP Index : 65538 TTM Tunnel Id : 655364

From : fd00::5

To : fd00::3

Adm State : Up Oper State : Up

LSP Up Time : 0d 00:06:50 LSP Down Time : 0d 00:00:00

Transitions : 1 Path Changes : 1

Retry Limit : 0 Retry Timer : 30 sec

Hop Limit : 255 Negotiated MTU : 8902

PathCompMethod : local-cspf

FallbkPathComp : not-applicable

Metric : N/A Metric Type : te

Local Sr Protec*: preferred Label Stack Reduction: Disabled

Load Bal Wt : N/A ClassForwarding : Disabled

Include Grps : Exclude Grps :

None None

Egress Stats : Disabled

BFD Template : None BFD Ping Intvl : N/A

BFD Enable : False BFD Failure-action : None

WaitForUpTimer : 4

ReturnPathLabel : None

BFD Source Addr : None

Revert Timer : Disabled Next Revert In : N/A

Entropy Label : Enabled+ Oper Entropy Label : Enabled

Negotiated EL : Disabled Override Tunnel ELC : Disabled

VprnAutoBind : Enabled

IGP Shortcut : Enabled BGP Shortcut : Enabled

IGP LFA : Disabled IGP Rel Metric : Disabled

AllowSrOverSrte : Disabled

BGPTransTun : Enabled

Oper Metric : 16777215

PCE Report : Disabled+

PCE Control : Disabled

Max SR Labels : 5 Additional FRR Labels: 2

Binding SID : 0

Path Profile : None

Admin Tags : None

Primary(a) : local-cspf

Up Time : 0d 00:06:51

Bandwidth : 0 Mbps

=====================================================================

* indicates that the corresponding row element may have been truncated.

*A:PE5#

*A:PE5# show router mpls sr-te-lsp family ipv6 path detail

=====================================================================

MPLS SR-TE LSP

Path (Detail)

=====================================================================

Legend :

S - Strict L - Loose

A-SID - Adjacency SID N-SID - Node SID

+ - Inherited

=====================================================================

LSP SR-TE tope3-ipv6

Path local-cspf

---------------------------------------------------------------------

LSP Name : tope3-ipv6

Path LSP ID : 13824

From : fd00::5

To : fd00::3

Admin State : Up Oper State : Up

Path Name : local-cspf

Path Type : Primary

Path Admin : Up Path Oper : Up

Path Up Time : 0d 00:07:11 Path Down Time : 0d 00:00:00

Retry Limit : 0 Retry Timer : 30 sec

Retry Attempt : 0 Next Retry In : 0 sec

PathCompMethod : local-cspf OperPathCompMethod: local-cspf

MetricType : te Oper MetricType : te

LocalSrProt : preferred Oper LocalSrProt : preferred

LabelStackRed : Disabled Oper LabelStackRed: Disabled

Bandwidth : No Reservation Oper Bandwidth : 0 Mbps

Hop Limit : 255 Oper HopLimit : 255

Setup Priority : 7 Oper SetupPriority: 7

Hold Priority : 0 Oper HoldPriority : 0

DelayMetricLimit : No limit OperDelayMetricLim: N/A

Inter-area : N/A

PCE Updt ID : 0 PCE Updt State : None

PCE Upd Fail Code: noError

PCE Report : Disabled+ Oper PCE Report : Disabled

PCE Control : Disabled Oper PCE Control : Disabled

Include Groups : Oper IncludeGroups:

None None

Exclude Groups : Oper ExcludeGroups:

None None

Last Resignal : n/a

IGP/TE/Del Metric: 40 Oper Metric : 16777215

Oper MTU : 8902 Path Trans : 1

Degraded : False

Failure Code : noError

Failure Node : n/a

Explicit Hops :

No Hops Specified

Actual Hops :

fd00:10:5:1::1

(fd00::1)(A-SID)

Record Label : 524281

fd00:10:1:11::11

-> (fd00::11)(A-SID)

Record Label : 524276

fd00:10:13:11::13

-> (fd00::13)(A-SID)

Record Label : 524285

fd00:10:13:3::3

-> (fd00::3)(A-SID)

Record Label : 524286

BFD Configuration and State

Template : None Ping Interval : N/A

Enable : False State : notApplicable

ReturnPathLabel : None

BFD Source Addr : None

WaitForUpTimer : 4 sec OperWaitForUpTimer: 0 sec

WaitForUpTmLeft : 0

StartFail Rsn : N/A

=====================================================================

Thursday, March 12, 2026

Flex-Algo Configuring on Nokia 7750 SR and steering VPRN traffic via Flex-algo 129 : A Step-by-Step Implementation Guide

Flex Algo provides the mechanism for IGP to use constraint-based paths like RSVP or SR TE using ISIS or OSPF extensions. By default, ISIS uses default algorithm 0. Along with it, there are 128 to 255 algorithms supported in Nokia.

As of writing, Nokia does not support flex-algo 1. but it does supported by juniper because we have identified during a project to swap Juniper MX with Nokia 7750 SR

All the routers participating in the Flex Algorithm should have the same definition of how it should work.

Consider the SRGB block of 2000-3000. To reach prefix F1, index-1, algorithm 0, label is 2001, then we have prefix F2, index-101, algorithm 128 and to reach F2 label is 2101

Nokia supports Flex algo 128, 129 and 130.

By default the IGP cost-based tunnel travels through PE5 to PE3 via PE5-PE1-ASBR1-ASBR3-PE5.

Let's configure Flex Algo 129 based on delay and push the traffic towards PE5-PE5-PE2-ASBR2-ASBR4-PE4-PE3.

*A:PE5>config>router>fad>flex-algo$ metric-type

{igp|te-metric|delay}

We can map the flex algo to SR-MPLS as well or steer traffic to SR-TE.

Delay metric:

We can configure the delay metric statically or dynamically and advertise it in ISIS or OSPF.

Configuring the delay metric on the interface directly.

interface "PE1"

if-attribute

delay

static 100000

exit

no shutdown

exit

interface "PE6"

if-attribute

delay

static 10000

exit

no shutdown

exit

As per our topology, shortest path to reach the PE5 to PE3 is via PE1 through IGP metric calculation.

Propogating the delay in IGP

*A:PE5>config>router>isis# info

----------------------------------------------

level-capability level-2

area-id 49.0001

traffic-engineering-options

advertise-delay

application-link-attributes

exit

We can configure both static and dynamic delay together and have the option to configure which one we prefer. I am using a static delay. In a later blog, we will use the dynamic delay calculation using twamp.

Configuring the flex algo and metric-type

ISIS advertising flex algo 129 and delay as metric type

A:PE3>conf>router>segment-routing# info

sr-mpls

prefix-sids "system"

ipv4-sid index 13

flex-algo 129

ipv4-sid index 53

exit

sr-policies

shutdown

reserved-label-block "sr-policy"

exit

A:PE3>conf>router>segment-routing# sr-mpls prefix-sids "system"

A:PE3>config>router>segment-routing>sr-mpls>prefix-sids# flex-algo 129 no ipv

ipv4-sid ipv6-sid

A:PE3>config>router>segment-routing>sr-mpls>prefix-sids# flex-algo 129 no ipv4-sid

*A:PE3>config>router>segment-routing>sr-mpls>prefix-sids# info

----------------------------------------------

ipv4-sid index 13

flex-algo 129

exit

----------------------------------------------

*A:PE3>config>router>segment-routing>sr-mpls>prefix-sids# no flex-algo 129

*A:PE3>config>router>isis# interface "system" flex-algo

<[128..255]>

*A:PE3>config>router>isis# interface "system" flex-algo 129

ipv4-node-sid ipv6-node-sid

*A:PE3>config>router>isis# interface "system" flex-algo 129 ipv4-node-sid

index <[0..4294967295]>

label <[0..4294967295]>

*A:PE3>config>router>isis# interface "system" flex-algo 129 ipv4-node-sid index 53

A:PE3>config>router>isis# info

interface "system"

level-capability level-2

passive

flex-algo 129

ipv4-node-sid index 53

exit

no shutdown

exit

*A:PE2>conf>router>segment-routing# sr-mpls prefix-sids "system" no flex-algo 129

*A:PE2>conf>router>segment-routing#

*A:PE2>conf>router>segment-routing# /co

configure compare

*A:PE2>conf>router>segment-routing# /conrouter is

Error: Bad command.

*A:PE2>conf>router>segment-routing# /configure router isis 1

*A:PE2>config>router>isis# interface "system" flex-algo

<[128..255]>

*A:PE2>config>router>isis# interface "system" flex-algo 129

ipv4-node-sid ipv6-node-sid

*A:PE2>config>router>isis# interface "system" flex-algo 129 ipv4-node-sid index 52

After swapping the flex-algo index from shared sid to system interface under isis. Route-table is populated with routes. Output below

A:PE5# show router tunnel-table

===============================================================================

IPv4 Tunnel Table (Router: Base)

===============================================================================

Destination Owner Encap TunnelId Pref Nexthop Metric

Color

-------------------------------------------------------------------------------

1.0.0.1/32 [L] isis (1) MPLS 524359 11 10.1.5.1 10

1.0.0.2/32 [L] isis (1) MPLS 524372 11 10.1.5.1 20

1.0.0.2/32 isis (1) MPLS 524379 11 10.5.6.6 18000

From below output we need to fix the PE4 to advertise the flex algo 129 route properly

After remapping the flex-algo node index under the ISIS context, now we see tunnel table entries separately for algo 0 and algo 129.

Steering traffic using an auto-bind tunnel, or we can use the Flex algorithm label used for 129 under path in SR-TE.

Let's use an auto-bind tunnel via VPRN service and make it work end to end to use flex-algo for VPRN traffic

Now we can see that for the PE3 destination, we have SR-ISIS flex-algo 129 tunnel based on delay installed.

Wednesday, March 18, 2026

Implemeting SR-MPLS Tunnel over IPV6 Network Core in Nokia 7750 SR

lsp "tope3-ipv6" sr-te to fd00::3 path-computation-method local-cspf metric-type te max-sr-labels 5 additional-frr-labels 2 primary "local-cspf" exit no shutdown exit no shutdown

Thursday, March 12, 2026

Flex-Algo Configuring on Nokia 7750 SR and steering VPRN traffic via Flex-algo 129 : A Step-by-Step Implementation Guide

lsp "tope3-ipv6" sr-te
to fd00::3
path-computation-method local-cspf
metric-type te
max-sr-labels 5 additional-frr-labels 2
primary "local-cspf"
exit
no shutdown
exit
no shutdown