Cumulus Linux 2.5.3

v
Cumulus®
Linux®
2.5.3
What’s New and Different since 2.5.0 (Technical)
Last Updated: June 18, 2015

cumulusnetworks.com 2
•BFD additions
•BGP improvements
•Hardware watchdog support
•LACP bypass with multiple active
interfaces
•Licensing change
•Resilient hashing
•jdoo replaces monit
•New hardware platforms
What’s New and Different in Cumulus Linux 2.5.3 vs. 2.5.0

BFD Enhancements in Quagga
 2.5.3 brings another way of enabling BFD
 Enable BFD in Quagga without a topology file
• (which was the only method until 2.5.3)
 ptmd is the underlying process in both methods
 OSPF
quagga(config)# interface <interface name>
quagga(config-if)# ip ospf bfd
 BGP
quagga(config)# router bgp X
quagga(config-router)# neighbor <neighbor ip> bfd
Simpler Configuration

BFD for IPv6 Peers
New “afi” topology file parameter
 3 supported values:
Global and link-local IPv6 address peering
supported using Quagga method
 Topology file method supports link-local address BFD
peering but not global
Value Description
v4 session built only for IPv4 connected peer (default)
v6 session built only for IPv6 link-local connected peer
both session built for both IPv4 and IPv6 link-local peers

BFD Multihop
BFD multihop enables BFD across arbitrary
paths between two systems
 Multihop is supported via Quagga
• Topology file method doesn’t support multihop
 Multihop sessions can use IPv4 or IPv6

BFD — ptmctl
ptmctl output has been enhanced
 Session type shows “multihop” or “singlehop”
 Source “local” address has been added to ptmctl
outputs for multihop sessions

BGP Improvements
2.5.3 includes several BGP enhancements
 Internal/external syntax additions
 Unnumbered interfaces
• (extended next-hop encoding)
 New interface configuration

BGP — Internal/External Peering Syntax
Before 2.5.3, BGP peering established using
neighbor x.x.x.x remote-as <ASN>
New syntax
neighbor (ipv4 addr|ipv6 addr|word)
remote-as (<1-
4294967295>|internal|external)
internal and external keywords enable
simpler automation configurations
 No need to know peer’s ASN

BGP — Unnumbered Interfaces
BGP unnumbered interfaces
 Enables BGP peering using interface names instead
of IP addresses
 Works with both IPv4 and IPv6 prefixes
 Works with IPv4 interface address if it’s a /30 or /31
address or over IPv6 link-local only
 Uses extended next-hop encoding (RFC 5549) to
exchange IPv4 prefixes over IPv6 link-local session

New
outputs
# show ip bgp
BGP table version is 66, local router ID is 6.0.0.5
Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
i internal, r RIB-failure, S Stale, R Removed
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 6.0.0.5/32 0.0.0.0 0 32768 ?
*= 6.0.0.6/32 swp2 0 65534 64503 ?
*= swp6 0 65002 64503 ?
*= swp5 0 65001 64503 ?
*= swp1 0 65534 64503 ?
*= swp4 0 65534 64503 ?
*> swp3 0 65534 64503 ?
# show ip route
Codes: K - kernel route, C - connected, S - static, R - RIP,
O - OSPF, I - IS-IS, B - BGP, A - Babel, T - Table,
> - selected route, * - FIB route
K>* 0.0.0.0/0 via 192.168.0.2, eth0
C>* 6.0.0.5/32 is directly connected, lo
B>* 6.0.0.6/32 [20/0] via fe80::202:ff:fe00:45, swp3, 00:46:12
* via fe80::202:ff:fe00:35, swp1, 00:46:12
* via fe80::202:ff:fe00:3d, swp2, 00:46:12
* via fe80::202:ff:fe00:4d, swp4, 00:46:12
* via fe80::202:ff:fe00:55, swp5, 00:46:12
* via fe80::202:ff:fe00:5a, swp6, 00:46:12

Example and config
 BGP interface configuration requires
enabling IPv6 ND router-advertisement
#New Configuration
router bgp 500
bgp router-id 10.0.0.1
neighbor EBGP peer-group
neighbor EBGP remote-as external
neighbor swp1 interface
neighbor swp1 peer-group EBGP
neighbor swp1 capability extended-nexthop
interface swp1
no ipv6 nd suppress-ra
ipv6 nd ra-interval
IPv6
IPv4

BGP — Interface Configuration
Allows for peering without using peer’s IP in
configuration
With BGP unnumbered interfaces, enables generic
BGP configs instead of configuring BGP on node-by-
node basis
 IPv6 link-local address-based peering for both IPv4 and IPv6
prefixes
• No IPv4 addresses can be assigned
 IPv4 interface address-based peering for IPv4 prefixes and IPv6
link-local address for IPv6 prefixes
• Simplified peer configuration is available when using /30 or /31 IPv4
subnets

BGP — Interface Configuration with IPv6 Link-local Peering
Configuration Details
Without an IPv4 or IPv6
global address configured
on the peering interface
• IPv6 prefixes will use IPv6 link-local next-hops
• IPv4 prefixes will use BGP unnumbered interfaces if
configured
IPv4 addresses
configured on peering
interface
• IPv4 prefixes will use IPv4 next-hops
IPv6 global address
configured on peering
interface
• IPv6 prefixes can use either global or link-local next-
hops
• IPv4 prefixes will use an IPv4 next-hop address
unless IPv4 is not configured on the interface, then
IPv4 prefixes will use IPv6 link-local next-hops

BGP — Interface Configuration with IPv4 Addresses
Interface-based peering logic
Configuration Details
With a /30 or /31 subnet IPv4 address configured • Peering is done using IPv4 addresses
• IPv4 prefixes exchanged using IPv4
address and IPv6 prefixes exchanged
using the IPv6 addresses (link-local if no
v6 address configured)
With no IPv4 address configured and extended
next-hop encoding not enabled
• IPv6 link-local address-based peering is
established
• Only IPv6 prefixes are exchanged
If no IPv4 address configured but extended
nexthop capability is enabled and supported by
the peer
• IPv6 link-local address-based peering is
established
• IPv4 and IPv6 prefixes are exchanged

BGP — Interface Configuration with IPv4 Addresses
To configure an interface IPv4 address and
still utilize interface-based peering based on
IPv6 link-local address, use the v6only
option
router bgp 500
neighbor swp1 interface v6only

BGP — Internal/External Peers and Interface Peering
Example config
 Much simpler config for automating.
 No need to configure neighbor’s ASN or IP!
#New in 2.5.3
router bgp 500
IPv6
IPv4

Combining BGP internal/external, Interface Peering and BGP
Unnumbered
Combined cleaner config
#New Configuration
router bgp 500
neighbor swp1 capability extended-nexthop
interface swp1
no ipv6 nd suppress-ra
ipv6 nd ra-interval
IPv6
IPv4

Platform Watchdog
A hardware monitor is needed to validate a
switch so it doesn’t become brain dead
Cumulus Linux includes a simplified version of
the wd_keepalive daemon from the standard
Debian package watchdog
How it’s used
 A daemon writes to /dev/watchdog at least once per
minute
 If there is not a write within one minute, the switch resetscumulusnetworks.com 18

Using the Watchdog Feature
To enable the hardware watchdog:
 Disabled by default on all platforms except QuantaMesh BMS T1048-
LB9
 Edit /etc/watchdog.d/<your_platform>
 Set run_watchdog = 1
To disable the watchdog:
 Edit /etc/watchdog.d/<your_platform>
 Set run_watchdog = 0
Then stop/start or restart the daemon:
 cumulus@switch:~$ sudo service wd_keepalive stop/start |
restart

LACP Bypass
LACP bypass
 Allows a bond to become active and forward traffic
without an LACP partner
 Extensions to LACP bypass allow multiple links active
in a LACP bond in bypass mode
During PXE boot of a new server
 LACP bypass allows a link to pass traffic (become
active) before the server can form an LACP bond
 Some boot systems require all links to be up during
bypass, and if both links are not active, PXE will not
execute

LACP Bypass
Example and config
auto esx-server3
iface esx-server3
bond-slaves swp11 swp12
bond-mode 802.3ad
bond-miimon 100
bond-lacp-rate 1
bond-lacp-bypass-allow 1
bond-lacp-bypass-all-active 1
mtu 9000
bond-xmit-hash-policy layer3+4
bond-lacp-bypass-allow 1
bond-lacp-bypass-all-active 1
Enable LACP bypass
Allow all links of bond to “bypass”

Licensing Change
New license format for 2.5.3 and later
How it’s used
 Single line license file
 New location: /etc/cumulus/.license
What does this mean?
 Old licenses will still work with 2.5.3
 New license incompatible with versions older than
2.5.3 cumulusnetworks.com 22

Resilient ECMP Hashing
 Ensures minimal disruption in flows when adding or
removing a link
 Achieved by keeping a flow mapped to its current link if any new
member is added or removed
 To configure resilient hashing:
• Edit /etc/cumulus/datapath/traffic.conf
• Enable by setting
resilient_hash_enable = TRUE
• Restart switchd
sudo service switchd restart
 To verify the configuration change:
cumulus@switch:~$ sudo cl-cfg -a switchd | grep resilient
traffic.resilient_hash_entries_ecmp = 256
traffic.resilient_hash_enable = TRUE

Resilient ECMP Hashing
Supported only under certain circumstances
 Trident II chipsets
• Check cumulusnetworks.com/hcl/ or run netshow system
 Unicast traffic
 ECMP groups
 IPv4 routes

jdoo replaces monit
Starting in 2.5.2 monit was replaced with jdoo
 jdoo forked from monit
 jdoo is a monitoring utility used to validate things like CPU,
memory and uptime for services
 jdoo can execute causal actions for error situations, restart
a process that does not respond, if it uses too many
resources
 Files, directories and file systems can all be monitored for
changes to existing timestamps, checksum, etc.
Change made because of licensing conflicts with
monit cumulusnetworks.com 25

© 2015 Cumulus Networks. Cumulus Networks, the Cumulus Networks Logo, and Cumulus Linux are trademarks or registered trademarks of Cumulus Networks, Inc. or its affiliates in
the U.S. and other countries. Other names may be trademarks of their respective owners. The registered trademark Linux® is used pursuant to a sublicense from LMI, the exclusive
licensee of Linus Torvalds, owner of the mark on a world-wide basis.
ThankYou!

Cumulus Linux 2.5.3

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