RPi5-PTP-server/NEXUS.md

# Cisco Nexus C93180LC-EX PTP Boundary Clock

NYATER is the second boundary clock in the PTP chain.

```text
RPi5 GM
  │
  ▼
WOLF-HUNTER BC
  │              │
  │ two QSFP+    │
  ▼              ▼
Eth1/5        Eth1/6
      NYATER
 C93180LC-EX BC
      │
      ├─ PTP client-facing ports
      └─ PTP client-facing ports
```

With the current design:

```text
RPi5            stepsRemoved 0
WOLF-HUNTER     stepsRemoved 1
NYATER          stepsRemoved 2
Linux client    stepsRemoved 3
```

The current Nexus configuration is stored in `NYATER.ios` in the root of the PTP directory.

## 1. Base configuration

`NYATER.ios` contains:

```text
feature ptp

ptp device-type boundary-clock
ptp domain 0
ptp source 10.255.254.255

interface Ethernet1/5
  ptp

interface Ethernet1/6
  ptp
```

`10.255.254.255` is the address selected as the Nexus PTP source address. In this setup it is the `lo0` address; using the loopback gives PTP packets originated by NYATER a stable source address independent of which physical upstream path is selected.

Before applying the PTP config, verify that the address really exists on NYATER:

```text
show ip interface brief | include 10.255.254.255
show running-config interface loopback0
```

## 2. Apply the base PTP configuration

Enter configuration mode and apply the contents of `NYATER.ios`, or paste the equivalent configuration manually:

```text
configure terminal

feature ptp

ptp device-type boundary-clock
ptp domain 0
ptp source 10.255.254.255

interface Ethernet1/5
  ptp

interface Ethernet1/6
  ptp

end
copy running-config startup-config
```

`Ethernet1/5` and `Ethernet1/6` are the two links from WOLF-HUNTER's Mellanox ports.

## 3. Expected upstream behavior

When both WOLF-HUNTER links are healthy, NYATER should select one as the active upstream PTP port and leave the other as the redundant path.

Expected output:

```text
show ptp brief

PTP port status
-----------------------------------
Port                  State
--------------------- ------------
Eth1/5                Slave
Eth1/6                Passive
```

The exact choice may be reversed; `Eth1/6 Slave` and `Eth1/5 Passive` is equally valid.

The important points are:

```text
- one WOLF-facing port is Slave
- the other WOLF-facing port is Passive
- PTP Clock state is Locked
- grandmaster identity is still the RPi5
- steps removed is 2
- domain is 0
- UTC offset received in Announce packets is 37
```

## 4. Add a downstream PTP client

For a normal Linux server connected directly to a physical Nexus port, enable PTP on that port:

```text
configure terminal

interface Ethernet1/<clientPort>
  ptp

end
copy running-config startup-config
```

For example:

```text
interface Ethernet1/10
  ptp
```

No separate per-client PTP source address is required. The existing global:

```text
ptp source 10.255.254.255
```

continues to be used by NYATER.

Once the downstream Linux client is active and the Nexus is locked upstream, that client-facing port should normally appear as `Master`.

Example:

```text
show ptp brief

Eth1/5     Slave
Eth1/6     Passive
Eth1/10    Master
```

Repeat only the interface-level `ptp` command for every additional direct downstream client port.

## 5. Verification commands

The most useful operational commands are:

```text
show ptp clock
show ptp brief
show ptp packet
```

Your healthy output should resemble:

```text
PTP Device Type        : boundary-clock
PTP Source IP Address  : 10.255.254.255
Clock Domain           : 0
PTP Clock state        : Locked
Steps removed          : 2
```

`show ptp packet` is useful for confirming that Announce packets still carry the RPi5 grandmaster identity and the expected UTC offset:

```text
gm_id=<RPi5 clock identity>
utc_offset=37
```

It also exposes Sync, Follow_Up, Delay_Req and Delay_Resp traffic and is useful when investigating offset or path-delay behavior.

## 6. Current known-good state

A known-good state observed on NYATER had:

```text
PTP Device Type       : boundary-clock
PTP Source IP Address : 10.255.254.255
Clock Domain          : 0
PTP Clock state       : Locked
Steps removed         : 2
Eth1/5                : Slave
Eth1/6                : Passive
gm_id                 : 88a29efffe826ce6
utc_offset            : 37
```

Use that as a topology sanity check. The active/passive physical ports may swap, but the grandmaster identity should not change merely because the redundant path changes.

## 7. What the `ptp source` address does

The `ptp source 10.255.254.255` setting selects the source IP address used by PTP/UDP packets originated by NYATER. It does **not** mean the Nexus gets its time from `lo0`.

The actual timing reference is still selected by PTP/BMCA through the WOLF-HUNTER-facing ports:

```text
RPi5 -> WOLF-HUNTER -> NYATER
```

## 8. Troubleshooting

If NYATER is not locked:

```text
show ptp clock
show ptp brief
show ptp packet
show interface Ethernet1/5
show interface Ethernet1/6
```

Check that:

```text
- `feature ptp` is enabled
- domain is 0 everywhere
- both WOLF-facing ports have `ptp`
- one upstream port receives Announce/Sync packets
- the received gm_id is the RPi5 identity
- WOLF-HUNTER itself is synchronized upstream
```

If a downstream client is not synchronizing, first confirm its Nexus port has the interface-level `ptp` command and appears as `Master` in `show ptp brief`.