Junos OS

Hi..

just wanna check...what does flap means and what is the different of flap and what causes of flapping (physical, power failure/reboot,???)

1. show interface fe-x/x/x detail (flap status in interface)

2. show bgp neighbor (flap status in bgp)

if interface flap ...does bgp also will show flapping?

does is down the services? 

I hope someone could make me clear on this...thank you.

Flap just means, an interface goes down and comes up again. Or a BGP session is lost and reconnected again. Usually a high flap rate indicates that something is going on.

Regards,

Dominik

Hi Domicik,

if interface flap does is mean the routing protocol also will flap? how can i check the previous status of that interface (up/down)...?

If you run e.g. OSPF over that interface or BGP - yes, the link down event will be sent to the routing protocol daemon that recalculates is LSD or drops routes that have that their next-hop rechable over that interface and so on.

Regards,
Dominik

Thanks Dominik...how can i check the log status of that interface..i want to know what time it up and down... i check using 'show log ....' but it didnt shw anything on the interface...

how can i check up/down log of particular interface...?

thank you in advanced..

Hi,

a down event will cause the following entry in the messages log file (provided you kept the default settings):

Sep 21 17:56:29  labswitch01 mib2d[856]: SNMP_TRAP_LINK_DOWN: ifIndex 506, ifAdminStatus up(1), ifOperStatus down(2), ifName ge-0/0/1

You could therefore issue a command like this:

> show log messages | match SNMP_TRAP_LINK_DOWN

To filter all these entries. For a specific interfaces, you could type:

> show interfaces ge-0/0/1
Physical interface: ge-0/0/1, Enabled, Physical link is Up
  Interface index: 130, SNMP ifIndex: 506
  Link-level type: Ethernet, MTU: 1514, Speed: Auto, Duplex: Auto,
  BPDU Error: None, MAC-REWRITE Error: None, Loopback: Disabled,
  Source filtering: Disabled, Flow control: Enabled, Auto-negotiation: Enabled,
  Remote fault: Online
  Device flags   : Present Running
  Interface flags: SNMP-Traps Internal: 0x0
  Link flags     : None
  CoS queues     : 8 supported, 8 maximum usable queues
  Current address: 00:26:88:7c:a0:41, Hardware address: 00:26:88:7c:a0:41
  Last flapped   : 2010-09-23 17:54:25 CEST (4d 07:35 ago)  Input rate     : 0 bps (0 pps)
  Output rate    : 0 bps (0 pps)
  Active alarms  : None
  Active defects : None

To see the last flap.

Regards,

Dominik

Thanks Dominik for your kind assistance....very appreciate it. ... 

Hi.

May I know why the time in last flap and the time in SNMP down is so different ?

Hi,

A flap is basically interfacing going down and coming up (a sudden off-on pattern) thus the timing of interface coming up is considered as last flpaped time. 

We will have many interface down logs. Each time the interface goes down the log is captured. So we will have many such instances. 

user@R1> show log messages | match SNMP_TRAP_LINK_DOWN | match xe-1/0/0
Feb 4 19:40:01.137 jtac-mx240-r2025-re0 mib2d[6060]: %DAEMON-4-SNMP_TRAP_LINK_DOWN: ifIndex 559, ifAdminStatus down(2), ifOperStatus down(2), ifName xe-1/0/0
Feb 4 19:40:29.937 jtac-mx240-r2025-re0 mib2d[6060]: %DAEMON-4-SNMP_TRAP_LINK_DOWN: ifIndex 559, ifAdminStatus down(2), ifOperStatus down(2), ifName xe-1/0/0
Feb 4 19:50:55.937 jtac-mx240-r2025-re0 mib2d[6060]: %DAEMON-4-SNMP_TRAP_LINK_DOWN: ifIndex 559, ifAdminStatus down(2), ifOperStatus down(2), ifName xe-1/0/0

user@R1> show log messages | match SNMP_TRAP_LINK_UP | match xe-1/0/0
Feb 4 19:40:11.337 jtac-mx240-r2025-re0 mib2d[6060]: %DAEMON-5-SNMP_TRAP_LINK_UP: ifIndex 559, ifAdminStatus up(1), ifOperStatus up(1), ifName xe-1/0/0
Feb 4 19:50:38.437 jtac-mx240-r2025-re0 mib2d[6060]: %DAEMON-5-SNMP_TRAP_LINK_UP: ifIndex 559, ifAdminStatus up(1), ifOperStatus up(1), ifName xe-1/0/0
Feb 4 19:51:42.437 jtac-mx240-r2025-re0 mib2d[6060]: %DAEMON-5-SNMP_TRAP_LINK_UP: ifIndex 559, ifAdminStatus up(1), ifOperStatus up(1), ifName xe-1/0/0

But if we see the latest flap from the log (Bold letters) that shows exactly what we see in the interface output as last flapped(Bold letters):

user@R1> show interfaces xe-1/0/0
Physical interface: xe-1/0/0, Enabled, Physical link is Up
Interface index: 150, SNMP ifIndex: 559
Link-level type: Ethernet, MTU: 1514, MRU: 1522, LAN-PHY mode, Speed: 10Gbps, BPDU Error: None, Loop Detect PDU Error: None, MAC-REWRITE Error: None, Loopback: None,
Source filtering: Disabled, Flow control: Enabled, Speed Configuration: Auto
Pad to minimum frame size: Disabled
Device flags : Present Running
Interface flags: SNMP-Traps Internal: 0x4000
Link flags : None
CoS queues : 8 supported, 8 maximum usable queues
Current address: d0:07:ca:8c:3a:d5, Hardware address: d0:07:ca:8c:3a:d5
Last flapped : 2020-02-04 19:51:42 CST (00:03:58 ago)
Input rate : 0 bps (0 pps)
Output rate : 0 bps (0 pps)
Active alarms : None
Active defects : None
PCS statistics Seconds
Bit errors 1
Errored blocks 1
Link Degrade :
Link Monitoring : Disable
Interface transmit statistics: Disabled

Logical interface xe-1/0/0.0 (Index 325) (SNMP ifIndex 3642)
Flags: Up SNMP-Traps 0x4004000 Encapsulation: ENET2
Input packets : 0
Output packets: 1
Protocol inet, MTU: 1500
Max nh cache: 75000, New hold nh limit: 75000, Curr nh cnt: 0, Curr new hold cnt: 0, NH drop cnt: 0
Flags: Sendbcast-pkt-to-re
Addresses, Flags: Is-Preferred Is-Primary
Destination: 172.168.1.0/30, Local: 172.168.1.2, Broadcast: 172.168.1.3
Protocol multiservice, MTU: Unlimited
Flags: Is-Primary.

We can compare a flap to door-bell. Ding-dong together makes a door bell sound. If a kid makes Ding...... and waits a bit and then release button making a Dong, we consider dong as end of door bell sound. 

Give a "kudos" if I deserve. 

If you feel this well answered your query please flag my post as an "Accepted Solution" so others can benefit..

Regards,

Rajat